3 months are not enough to revert the impact of 15 years. It's like having 3 hours of weekend, after 6 days and 21 hours of workweek -- you wouldn't feel refreshed either. If you can afford it, give it more time: a year or two.

In the meanwhile, try other things. Do you have hobbies? If no, did you have any when you were a child? Or just experiment with new stuff.

Or perhaps try finding a place where your computer skills will be useful, but you wouldn't be doing the classical kind of development. For example, you could help some people in their work by creating a spreadsheet with automatically calculated results. Or try writing documentation for open-source software. Teach kids programming or using the computer.

Without knowing more about you I can't give a better advice. But the main message is that after 15 years of doing something, 3 months of break do not mean anything. Especially if you spent them taking care about a small child; that is not the same as having a break fully for yourself.