Major stomach problems... I need some help.?

So I've been experiencing stomach issues for about 2 years now. It used to come in waves but now it's just all the time. It all started with eating bad food and I'd get diarrhea a lot. But then it would stop for like a year and then it would come back. I'd have to watch what I ate because of the diarrhea I'd get. But recently, at this beginning of this year, I've noticed how bad it's gotten. I ALWAYS have to watch what I eat now. I'm even on a diet and I eat SmartOnes from Weight Watchers. I used to think I was lactose intolerant. But now I'm just thinking it's something wrong with my stomach or intestines. I always have to watch what I eat because I'll have to run to the bathroom or run home. Is it IBS? Is it an ulcer? What the hell is wrong with me? I know I should go to a doctor to figure it out, but I'm just too scared. So I figure I'd get other people's opinions. Please help! Thanks.