Hi Dan,
I've been feeling the same way. I've been trying to be more active here and there doing things around the house or walking abit extra when I feel well, usually a few times per week. I do feel like I've lost my muscle tone. I see lumpiness everywhere which I am not used to. At this stage there isn't a whole lot we can do, I don't think they recommend taking up a new exercise at this stage in our pregnancies. Gentle exercise more frequently will help out though.