Fainting with weed

Hey everyone. So I use to be a daily smoker for about 5 years, I stopped smoking weed because I stopped craving it enough to stop picking up. So lately I have been having out with some old friends they smoke now right when I "stopped." What's been concerning me is that I have been fainting numerous times during/after smoking. I simply don't understand why I wasn't like this last year I use to tolerate it well but now I faint almost every time I smoke after 7 hints or so. Perhaps because I'm vegan with an extremely low iron levels, underweight, alcoholism, severe anxiety and high blood pressure.... however even before I knew I had anemia I didn't faint with weed. I have been heavy drinking and using coke almost daily for the past year but I don't see how that has to do with anything or perhaps maybe although pretty much anything makes me faint or get seizures. I literally have to smoke a cig, drink water and lay down for a while to return back to earth. I feel bummed because I can't "hang" anymore and can't give valid excuses to people when I get offered weed. And Its not that I smoke too fast or get too high.. Fainting scares the sh*t out of me and it's quite embarrassing because I can't chill with my friends anymore and have to reject weed to avoid getting myself sick or have people worrying about me. What could be going on though? (by the way I wouldn't be asking this question if anyone says I answered my question I just need some advice)