I did it just under 3 weeks after birth and I had an episiotomy. I remember it felt quite tight, nipped slightly and had to go slow but I didnt have any pain internally really. In hindsight I did it too soon but & I wouldnt recommend it.
Id have a word with your dr about it. It may be normal but its worth getting checked. My friend actually had something similar when she had sex with her ex in the 1st year after birth. She never went to dr but, and then split with her OH (not sex related at all btw!) Its been about 4 years since she was in a relationship and she does worry that it will reoccur when she having regular sex and wishes she had gone to see about it at the time. She said she would get shooting pains at top of her womb/tummy and have to stop. Hope your ok x