worried about being prego. this is coplicated

So i had sex for the first time. We used a condom and there were no tears or slipping at all. Plus he pulled out so that adds to the safety. I got worried about being prego so i did a test 2 weeks after we had sex and it came back negitive. But i felt like that was too early so i waited a 2 more weeks and did one again and got another negative. so about 3 days after i took that test i had oral surgery done to remove my wisdom teeth so i was on pain killers and during the recovery time i had my period. But it was an odd period because it was so light (ive never been normal, sometime ill skip 3 month and then have my period. but most of the time its pretty heavy or normal) Now im off the pain killers and all that. I feel bloated and i have constipation and diarrhea (varys from day to day) and cramps sometimes. im just worried and I know this sounds weird but has anybody noticed tha IBS smyptoms and pregnancy smyptoms are a lot alike? could i just have IBS?