I'm scared and don't know what to do, any advice?

Last Friday I was with my ex and we ended up having sex. We don't use condoms but he always pulls out. A few days later I had sex with a guy I was crushing on. We had sex three times that night and as far as I know he pulled out. Just yesterday I was back with my ex and realized that my period was late. I've never been late before so this has me concerned. As of today I am four days late and I don't know what to think let alone do. If anyone has any suggestions please feel free to comment. I'm kinda scared.