To cum or not to cum

I spent a weekend with a friend with benefits. I never had sex before so he was the fist one. In the whole weekend we had sex for like 6 times I think. Every time we did it with a condom on because we don’t want no baby.... To be honest from all the times we had sex I did not cum ones.... why? Is it that I have to start my period? Did I do something wrong? The sex felt good and I did not have pain or did not bleed. I enjoyed it. So it’s so confusing for me...