Anxious

I had unprotected sex with my boyfriend a while ago since he’s allergic to latex but I got my period a week and a half after that. We had sex again on Friday which was a day before my next period was due and I took plan b on Saturday. It’s been Monday and I haven’t seen my period. I took a pregnancy test and it was negative but I was unsure if it was too early to read correctly. Is it the plan b delaying my period or could I be pregnant.