Is it normal to feel guilty about going back to work?

Of course. Feelings of guilt when returning to work after having a baby are very normal. But, remember that having a life outside of parenthood does not make you a bad parent. You need to find your own balance. (make sure to avoid people who try to make you feel more guilty - they are not helpful.).
Guilt. I don't think it is abnormal to experience guilt when returning to work but your guilt is telling you something that is woth being aware of, for instance are you working too much, do you regret leaving your family etc.