33 weeks pregnant cramps??

I’m a FTM (first time mom) and don’t know what’s okay or what’s not, this does not happen every night but I wanna say this past month it has happened at least 4-5 times and only happens during the NIGHT. So it’s not because I’ve been moving or pushing my body to much I’m literally sleeping, I get these really really painful cramps in my lower stomach around my pelvic they really hurt to the point I’m moaning through the pain & rolling back and fourth sometimes it’ll last an hour or sometimes like lastnight it’ll last HOURS it lasted from 3:42am from 8am.. what is going on?? Why is this happening?