I have had tummy aches for over 3 weeks now?

It all started when I ate at one of my favorite resturants about 3 weeks ago. I got sick to my stomach with nausea, cramps, and diarreah. I thought maybe I had food poisoning, but I dont know if it lasts that long. Now when I get hungry I feel bad. After I eat I feel horrible. My bf thinks its IBS but Im not so sure. The nausea and cramps subside "some" if I take an antacid and drink a couple glasses of water. But I'm trying to drink a lot of water anyway because I think having the diarreah is dehydrating me. I dont make a lot of money and I dont have insurance, so going anywhere expensive isnt really an option. The clinic cant see me for another week. It was so bad this morning it reduced me to tears. I took 2 bites of sandwitch and began hurting again. Im so tired of hurting. Any tips or valid advice will be appreciated.