Weird cramp type pains

Bunny • ttc 4 years with 2miscarriages. Rainbow BABY GIRL born 3/10/18💕🌈 Gorgeous girl#2 born 02/19/19💕💕 baby #3 due 03/01/21
Ive noticed that everytime i go to an exhausting, face pace concert. or rollerblading i get these period type cramps, as if my uterus contracts. ive even started my period during some of these events. is this normal? im ttc & worried there might be something wrong