Bad lower back pain after sex?

Maybe TMI but I'm getting anxiety over the pain...My husband and I aren't as frisky as we were before getting pregnant (I'm 13 weeks 1 day) but today we had sex (I was on my back, feet resting on his shoulders--nothing crazy!) and about two hours after I have had very bad lower back pain. It's worse when I walk and is somewhat in my hips also. No cramping or anything else but I have been laying all day with no relief. Anyone else had anything like this before? Or weird symptoms after sex?