I think (from my recent experiences) that this is a continuation of the anxiety. As long as you are not overdoing it, I know exercise is so good for you! My doctor told me to get walking everyday, and I've been slacking the past few(many) days. But, I know it is healthy for mind and body!
Maybe call your doctor for reassurance and then don't be afraid to get back on that treadmill. You will be ok...
I have so much sympathy right now - it's hard!!!