Hi there. my boyfriend gets cracked on his penis foreskin after having sex, could it mean that i have an sti?

Not necessarily: It likely means he should consult with a urologist to find out how to fix his problem. It doesn't sound like a feature of a STI to me, however, he might have one anyway. I would use condoms until you sort this out & since the issue is on your mind having yourself tested is a good idea. There are STD's that can have few or no symptoms in either sex that can make you sterile.