I Recently Lost My Virginity In May, But Protection Was

I recently lost my virginity in May, but protection was used. I was worried that I would get pregnant. So I bought two pregnancy tests and took one, a week after the intercourse. And another, a month after the intercourse. Both came out negative. I also had a period. In addition, I participated in a study that required a pregnancy test which also came out negative. However, for the past few days, I've been experiencing stomach pains, nausea, bloating and heavy fluttery in my stomach. It's been 2 months, almost 3 now. So I was wondering could this just be gas or could it be a cryptic pregnancy??? Please help.