Pelvic pain

Maredith
I'm 27 weeks with #2, our first one was early and they think that this one will be early too. 
I had an ultrasound at 24 weeks to see how low he is and he is already head down but they said it wasn't a sign that he would be premature.
Now I have been having such strong pelvic pain and pressure that it makes me stop and bend over sometimes to recoup. I don't know if it is something I should be concerned about or not. 
When I mentioned it to my doctor three weeks ago, she said that my muscular would be different with each child but this feels too strong to me at this early