Strange things happening

Ok..I'm really concerned that I could be pregnant.

I had been taking the pill for months.  I think I missed one or two, but then took two together to "make up" for the missed pills.  In the following days I had sex, but a condom was used.  This was in the first week or two after getting my "period" on the pill.
Then, next time round, my "period" came early by a day.  This has never happened before.  The period was also quite heavy and brownish in colour and only lasted 3 days, with exceedingly light bleeding for the rest of the week.

After starting the next pack of pills, I decided I should stop going on the pill...so I just stopped taking them.  A week after finishing my period (three days without active pills) I got a period again!  Was really freaked out about this.  Again, the bleeding only lasted three days.

I took a home pregnancy test after this, which was negative.  I was still paranoid though

All month I had weird feelings like wind or something moving in my stomach...and tiredness (though this could be due to other stuff) and eating more too.  I'm not sure if there's frequent urination or if I'm just paying too much attention to when I go to the toilet.  But no morning sickness, nausea, breast tenderness or anything else noticeable. 

Now, it has been one month and two days since my last period (the last time I bled). I have not had sex in this time.  However, the usual PMS symptoms I got, both on and off the pill (they were getting less and less while on the pill, but were still there), have not surfaced as strongly.  I have had a bit o a sore back and a nasty pimple, but neither are as bad as they "usually" are.  Still not bleeding.

I am so freaked out...am I just being stupid and paranoid or could I possibly be pregnant?

I have also read on the internet that sometimes when you come of the pill your periods can be irregular...I just want to know ASAP if I am pregnant so I can act on it...

Thankyou.