Hey Sandy,
Hard to say really what that could be from ... but if i had to venture a guess i would say that it would probably be from all the stress of the surgery and things that you two have gone through in the past little while. Thats a lot for anyone to go through and so this could just be your body's way of telling you to slow down and try and relax a bit if you can.
There are however other things that it could be from, so like Juliana mentioned, you might want to make a doctor's appointment if it keeps up, or gets worse.
Hope you feel better soon,
Jacq