Do I have weak abdominal muscles?

I am 17 weeks pregnant and have gained 6 lbs. My BMI was normal when the pregnancy began (24, so high but still normal). I am already showing quite a bit, and the top of my belly on is starting to flatten out. My mom says that I need to ask my doctor about abdominal strengthening exercises because if my belly looks like this now it is going to be super hard to get back in shape after the pregnancy... so this obviously concerns me. The health of my baby concerns me more though, I'm just wondering if she could be right about my abs? I mean, I was in roller derby up to 2 months before I conceived, I don't think I could be in that rough of shape??