May sound crazy, but just an honest concern

I am a FTM, at 20 weeks today. If you've been pregnant before you probably know that sometimes it can bring constipation, right? Well, I've been constipated for a week & finally felt the urge to go. So of course, I'm taking the opportunity.. I had to push harder than normal & I always get freaked out that I'm going to push my baby out. This happened to a girl that I went to high school with, so ever since I have just always had it in the back of my mind. Can someone please make me feel like I am crazy & this won't happen?!?