I am aware there are more questions with the same title, but I couldn't find any other post with this specific case.
I have Xcode 7.0 and I want to update to the last version (7.3). But it doesn't appear in the updates page of the App Store. So, I searched for Xcode in the App Store and clicked the little update button. The button remains pressed and a loop icon appears on the top. But it stays like that for hours and there's no sign it's updating.
This doesn't seem to be working. I found in the internet that if I uninstall and reinstall it may work, but I don't want to lose all my projects.