At 13 weeks your uterus is still pretty far back, and your baby is.protected by all of the amniotic fluid. If there's no bleeding, PAINFUL cramping, then don't worry about it.
Schedule a doc appointment so you can hear the heart beat.
Oh god im so sorry to here that :( i would be scared i will krep you in my prayers but try not to worry if doctor said youre fine then that should be it :)