Can a tampon get stuck in your stomach?

No, a tampon cannot get into your uterus as the opening to the cervix (the bottom of the uterus) is too narrow for a tampon to get into. Your vaginal canal is essentially a dead-end as far as tampons are concerned, they can go no further than the vaginal canal. If you insert [clean] fingers vaginally you can feel for yourself that your vaginal canal is only so long ans there's nowhere for a tampon to go.