I took my mervelon pill on late Friday night and missed taking one on Saturday I had sex on Sunday morning and took a pill at 8.30 last night does this mean I could be pregnant

Yes, every time you have sex you could get pregnant, you will just have to wait and see if you get your period and if not then test.

Anytime you engage in sexual intercourse you run the risk of getting pregnant. While contraception reduces that risk, it doesn't eliminate it.

Since this was posted in Child & Teen Health, that indicates you may be underage. If you are concerned about getting pregnant, then why are you engaging in sexual intercourse?

Having sex while a Teen involves all sorts of issues, emotional, physical and legal.