What’s going on?

Niece

Hey ladies , I have a question hopefully someone can enlighten me. I lost my pills around the 28th of April. I didn’t start a new pack yet. It was week three and I missed about 4 pills. I had unprotected sex and started what I believe was breakthrough bleeding. My period is about 2 days late. Is this normal? I was only on birth control for about 2 1/2 weeks? Not a full 21 days. I was on Sprintec combination pills.