Aching pelvic muscles and back at 15 weeks, is this normal?

Gradually over the last few days, I’ve noticed my pelvic muscles aching, feeling stretched. I assume it’s because the uterus is growing, ligaments and muscles adapting, etc. But I just wanted to see if anyone else is experiencing this? I’m also insanely constipated at the same time, making it hard to know what is causing my pelvic discomfort.