Okay well i'm 16 and I have an uncircumsized penis.

My foreskin cannot retract easily and it is usually painful.

Me and girlfriend are planning on having sex,
so my question is,
during sex will I be in pain because of my foreskin not being able to retract?
Should I pull back my foreskin before sex? Or let it happen by itself??

Also when getting oral sex, my girlfriend pulls my foreskin back and it is somewhat painful, and it seems like my foreskin cuts off my blood circulation in my penis because sometimes I lose feeling in the head because of the tight foreskin on my shaft

can anyone answer my questions and give me tips on the tight foreskin problem?