First Pregnancy and PAINS

Abby • 👶🏼 Danny Lee 7/22/17 👼🏼 12/12/17 👶🏻 Deagon Levi 12/17/18 👶🏼 Daxxen 8/15/2020 Army wife 🇺🇸 Breastfeeding Mama 🤱🏼 Natural Birth Survivor x2
So I'm 21+4 with my first, and I have been having the absolute WORSE pains in my lower back and pelvis/hip bone area! I am a pretty tiny person so I feel like I should be more belly (I'm 5'2 125lbs) but I think he's sitting back so far is why I'm having these pains!? Help!