Help! Curiosities☯

I've had sex, and it's about once a week. We use spermicide, condoms and he always pulls out so I've never had any cum in me. But I'm still late and I've never been irregular except once! I'm not stressed out because i know i can't be pregnant. I was depressed for a few days a couple weeks ago. And about a week to two weeks ago, i started working out, not a lot but just a bit of toning (ex: squats and sit ups) and i went to a one hour fitness class last week. I'm just curious, why am i late??!