Hey I stumbled along this post. I've dealt with much of the same experiences you have. I used to smoke bud just about daily, as I was a freshman at college just livin' the high life. It was a lot of fun, and me and my roommates would all smoke together and go out and longboard or just BS around, you know -- the usual stuff.
Anyways, after about 7 months of heavy smoking, it was finals week and I took some concerta (ridalin) because I thought it would help me focus for my pre-calc final. I really wanted to do well. So anyways I took a 20mg pill and I didn't sleep at all that night, I just stayed up studying, and I didn't eat much either. I took another 20mg pill before my morning final and went and took my test. I aced it, but afterwards I felt kind of shaky. I just shrugged it off, like yeah, that's normal. So then I went and had a little victory smoke sesh with my roommates and friends and we went and smoked a glass blunt and a joint or two. I hadn't smoked all finals week, so I got super high. Then I started to get a little paranoid about being caught. The next thing I knew my heart was pounding insanely hard and fast, and I was like "guys, I'm done, I'm too high" , so I just tried to relax. But I kept thinking about my heartbeat, and it seemed like I was getting higher and higher. So I'm like guys I'm going back to my room.
So I went back to the dorm and then things took a turn for the worst. I started shaking and my heart was just pounding. It felt like I couldn't be still, even though I just wanted to so badly. I was starting to freak out, from all the adrenaline (no doubt) and I'm like alright maybe I can go run this off. So I went outside and started running, just running, to nowhere in particular. But I couldn't escape the thoughts of paranoia, and now my breaths were getting even shorter. So I started walking and I just felt crazy. I walked for blocks down this street trying to clear my head, and my body, but I was just getting more paranoid. Then I got to this crosswalk and I had a crazy experience, it was like I lost control of my thoughts and they started racing a million miles an hour, just like omg this is insane, im dying, wtf is happening, my heart is beating too fast, etc. and then I had like an outer body experience, the only way I can describe it is like I was viewing my life from third person, or it was like I was able to consciously thing "wow my mind is going crazy" while it was going crazy. That sounds weird, but that's the only way I can describe it.
Anyways, my friend called me, and he knew I was in trouble and I tried to back and sleep, but I just had this general feeling of restlessness, like I couldn't sit still. So he drove me around in his car with the music and we went to a park so I could try and calm down. It didn't really work. I was super close to checking myself into the university hospital, because I thought I was honestly going to die. So I ended calling my parents because I didn't know what else to do. I was still tripping out, and 10 hours later I drove home on the interstate. I couldn't even listen to music because idk it just was 'too much' for my mind. I drove super fast like 90mph the whole way.
Anyways that was the worst day of my life, and things continued to get worse. I ended up having panic attacks where i couldn't breathe and sh*t, and I just felt impending doom and I would just start crying. Too add to it, I started experiencing other physical things besides racing heart.. my chest would get super tight, my head and neck would get tight, and it would feel like my head was just constricting. I went to the ER one night and they gave me xanax. I went to a counselor and a dr and they put me on anti-depressants. I started on prozac, but that just made me feel even worse, and depression. I went through a month of pure f*****g hell. I itched on the inside, things went to fast and to slow, I felt no connection to anything.. Finally, I got a prescription to lexapro and it's done miracles for me. I've got my life back, and I've only had one minor panic attack -- when I woke up pretty hungover with the spins and my heart pounding. I was able to control it though, using breathing techniques and positive thoughts.
Just wanted to share. I thought I knew everything about marijuana.
Know your sh*t, don't mix bud and prescriptions, everyone reacts differently. And if you have anxiety, don't smoke anymore. And don't research anxiety and your symptoms on the interent, you will only get more paranoid hearing everyone else's stories.
Peace and good luck to everyone.