I have no clue

So I have been on birth control for almost a year now and have taken it regularly. But in April and May I had to take antibiotics and had unprotected sex. So I started feeling off in June. Nausea, fatigue, foods and drinks, normally love I can't have anymore and abdominal cramps( not bad). I have taken a couple over the counter pregnancy test and one came back positive but the rest negative. I had a blood test in early June and again that was negative. So i got it out of my mind. But I still have most of the symptom's and now my stomach is starting to round and tighten even though I haven't gained any weight Is it possible for me to be pregnant even if all the test say no?