We were in a pool I'm not sure if his penis went in me. He cummed 3 days before. I got my regulare period 5 days later that lasted a week. Could I be pregnant?

YES.
Stop playing with fire unless you want a child!!

Yes, of course - I have no idea what him "" 3 days before means. He certainly wasn't "out" of sperm!

If you had unprotected sex (and in theory his penis doesn't even have to enter you in order for you to become pregnant) you could be pregnant BUT you had your period AFTER this intercourse?

Am I correct?

Yes, I had my period 5 days after this happeened..

Well, if you had your period why do you think you are pregnant?

And before you have protected or unprotected sex again, why don't you go on line and learn how the mechanism of getting pregnant works - ? Knowing as little as you apparently do is a recipe for disaster.