Sever cramp like pain after orgasm i get this quite a lot just recently especially if i haven't orgasmed in a while it's really painful ?

Cervicitis: You may have Cervicitis due to chlamydia or mycoplasma or gonorrhea. I suggest you get a check up at a local STD clinic and ensure that if you turn up positive, your partner is also tested and treated appropriately. It could be something else I don't know about so consulting with an Ob Gyn would be a logical step if no STD is found.