Aching Uterus?

Kala • Married mama of 2, pregnant with rainbow baby due October 2018.
I'm 16 weeks +1 today and my uterus hurts. No, I'm not cramping and it's not those sharp round ligament pains...its just like this dull ache that doesn't go away. Is it growing pains or something? Haven't had it at all this pregnancy, but all day today it's just been really uncomfortable.