Since January 2015 And As Far As I Can Remember

Since January 2015 and as far as I can remember I haven't had a proper period as I usually would. Instead blood will come (a spray like), spotting and I feel as if I can feel my period coming but it doesn't. I got told it was because if poly cystic syndrome, my diet, antidepressant pills and stress. I've taken a pregnancy test in late Feb but it was negative and now family have worried me because the test was then and not now. My stomach is big and hangs (as my dad does too) although mine is quite heavy. Past two days I feel sick even though I want to eat so bad. I'm also a casual smoker (I'm thinking that's probably a reason why my body's playing up) Is there somehow a reason why this is happening?