IBS?

Hello
In mid July I had a very sharp pain from my lower right side traveling to my lower left side abdomen. I had just had a beer from a local bar and was eating crackers and salsa. The reason I am mentioning this is that as time has progress I felt that I might have picked up a bacteria and was not even thinking about IBS.
Another issue that had me going crazy was the fact that about a month earlier I had been with a woman and preformed unprotected oral sex.
I went and had all STD's tests done and all were negative. I also had a HIV test. The Hiv antibodies 1&2 test that is very accurate according to my doctor who is a infectious disease specialist. The test came back negative and I am going back in two weeks at the 90 day point to be retested. My doctor told me he has never had anyone come back positive after the first test. I did have diarrhea for one or two days but since then my BM's look normal.
My symptoms right now are stomach ache, bloating, and flatulence. There are times when I feel that I have to go to the bathroom but when I go I pass a lot of gas and little or no BM, However I do have a BM at least once a day.

Is this IBS or could it be a bacteria that I could have picked up from where I ate and drink or with the woman I was with?

any response is appreciated.