Penicillin and energy to workout

I had a root canal last Monday - not fun! I've been on penicillin ever since and have 3 days left to go.

The problem is, I've had such a lack of energy since the procedure. I've slept late every day and only gone for a walk once and done yoga once - I normally do both 4-5 days a week. I've not done even one workout - just thinking about picking up my lovely weights make me wanna nap.

I am really hoping it is the penicillin that is dragging me down but am feeling just awful mentally and physically.

Has anyone else had a similar experience, or should I be concerned?