Late period

I’m freaking out and need advice.

I had protected sex with my partner a few weeks ago. He wore a condom and he never finishes in me. He always pulls out and finishes himself. This time he did so with the condom still on. My issue is they my period is a week and a day late. BUT after we had sex I started my period the very next day. So I’ve had a period since then. My periods are very short because I’m on the birth control pill. But I don’t understand why my period is so late when he didn’t even finish in me at all, he wore a condom, pulled out, and I’m on the pill.

Part of me thought I was stressed or maybe did something different with my diet possibly but I’m freaking out a little bit because I’ve never been this late.