Why do i have stomach cramps and gas after my husband ejaculates inside of me.

May be vaginal: spasm,or cervical spasm secondary to orgasm. Try adequate lubrication and position changes and see if the symptoms resolve within 2 weeks.

Reaction: could be creating a reaction either from the cervix or the uterus best way to know is to change position and to see if you get the reaction in every position or only in specific one if you did get in every position try to use condom that way you know is it a reaction to the sperm or from the actual sexual experience not the sperm itself