Scaring myself ? Help please

I had sex about before I was supposed to start my period but sometimes they're irregular. The day after I had sex I had very very light blood come from me here and there. Didn't know if it was my period extra light cause it's usually medium or heavy or spotting. We didn't use a condom but I was on birth control but had accidentally skipped a day before that and took it hours before we had sex. We had sex about a week or so later unprotected and I was off birth control, he pulled out both times but my periods late and idk if it's just stress or because I started a new brand or birth control. I'm scaring myself, any tips or advice ?