Having read your post, I think you are connected symtoms that may not be connected; thus, I'm going to try & seperate what you've said & hopefully, shed some light on a few things for you.
The TMJ doesn't cause anxiety- it's the other way around. TMJ can be caused by having anxiety. Clicking & grinding the jaw is, in a way, the same as someone biting their nails; it's a reaction to anxiety that may not be 'obvious' to the person experiencing it- do you know what I mean here? I feel as if my words are a little mixed up today!
I know it's extremely painful sometimes- I was told I had that a good few years ago & last year, had to have 2 back teeth removed to ease it. I also had to wear a mouth-guard at night times, as I grind my teeth (there were holes in it within a week!) & have exercises to do when the pain gets too much (because as you probably know- painkillers rarely work!). I was also advised to stop biting things- I am quite orally fascinated, so everything tends to go in my mouth. I used to bite my nails down to the skin & chew pen-tops, but had to make a real conscious effort to stop doing.
I wouldn't necessarily connect the drinking to your TMJ- although, some drinkers who stop DO develop it, as a reaction to the anxiety they feel at stopping their addiction. But I want to ask (please don't be offended)- do you or have you ever smoked cannabis? Apparently, A LOT of cannabis smokers experience TMJ also (I was told this by a doctor & a dentist). I don't know the logistics of why cannabis smokers are likely to suffer with TMJ; I'm guessing it's connected to the anxiety that cannabis causes for some.
I'm going to guess that you've got a history of anxiety that preceeds your drinking & current stress.....and I'm also going to guess that the pressure in your head is caused by the tightened muscles at the back of your neck thats sending pain signals up in to your scalp. This may not necessarily be just the TMJ, but also another symptom of the stress you are going through.
To answer your other question: the symptoms of alcohol withdrawal are different for different people, but a few general characteristics are- dodgy stomach (diahorrea & nausea), shaking (known as the DT's- the detoxification trembles), altered appertite, disturbed sleep patterns, disturbances in short term memory, feelings of depression & anxiety, flu symptoms (including high temperture & aches & pains). They can last for a few days or a few weeks, depending on the person & how they are coping psychologically.
You are not alone in feeling the way you are. From what you've written, you are under a lot of stress & are having to deal with a lot on your own. You are a single-parent & by the sounds of it (taking in a lodger) are struggling to support yourself & your child, while having to deal with your son's father & also have some kind of life of your own. Additionally, if you suffer(ed) with PPD (post-partum depression), I'm guessing that life hasn't been a party for a while! You have had a hell of a lot to cope with.
I can definitely empathise here- single-parent myself, with an ass-hole for an ex; struggling financially & suffer(ed) with post-natal depression, among a few other disorders that are/were related to anxiety (i.e; panic attacks & OCD).
This post could be a long one, but I will try not to ramble on too much; however, I hope I can convey this clearly enough for you to gain some understanding of your condition, so that you can start to overcome it.
Growing up, we learn skills from our parents/careers/close family in how to deal with stressors. If we see 'bad' ways to deal with it- even small negative behaviours- we internalise them. Hence, if a child grows up in a household where their parents display neurotic behaviour to stress; the likelihood is that the child will also display these behaviours as an adult- or at least, behaviours similar to those of their parents. Coping skills are learned- they are not necessarily instrinsic. Drinking is a major coping strategy that is learned- whether it's learned through peer or family/career example. Thus, I'm going to guess that you started drinking as a way to cope with 'uneasy' or anxiety feelings and that your parents/careers didn't demonstrate healthy coping behaviours.
The TMJ is not neccesarily something you can control, unless you catch yourself clicking your jaw or grinding your teeth, which can be a hard thing to do! Hence, the best method of stopping it, is to deal with the cause of your anxiety & a change in coping strategies.
Have you been on any anti-depressents? Were you prescribed anything when diagnosed with PPD? How about therapy for your anxiety- is that something you've tried or would consider?
The unconnected bit of your situation is what you were experiencing when you had your knee injury. You have stated that you spent a lot of time on the floor on the computer. The pressure in your head that you were experiencing then may possibly have been down to the TMJ (as you were probably feeling quite stressed out at the time), but it's quite likely due to the fact that you spent a lot of time on the computer.
It sounds as if you carry your anxiety in your head & shoulders. I believe that people carry the physical effects of mental stress in different ways; some in their stomachs (hence, symptoms of IBS- irritable bowel syndrome- & butterfly feelings), some in their head, neck & eyes (hence, TMJ, migraines & headaches, shooting pains in the eyes & forehead headaches) and some in their energy levels (hence, tiredness, eye strain, lack of appertite or eating more).
I'd advise some relaxations strategies, such as yoga, aromatherapy and massage. These really help with TMJ symptoms and the mind feels better after a good relaxation session. Be careful about spending too much time hunched over a computer or slouched forward, as this can make TMJ worse.
And also, try and get some professional help for your anxiety. If you hit the core of your stress problems, the physical effects will start to fade. If you can't afford professional help, would you consider going down the self-help route? If you can, look up a therapy called CBT (cognitive-behavioural therapy). It's best done in a professional setting with a therapist, but there are certain strategies that you can look up and read about & perhaps incorporate in to your every day life. These strategies include relaxation techniques, time & emotional management plans & 'mantra's' (words & phrases to repeat when feeling an anxiety attack coming on).
Good luck & I hope you are able to get relief soon.
My best wishes to you.