Headspace problems can cause a lot of stuff, but unless you're measuring your fired brass vs. your resized brass, you could be over resizing your brass. Headspace is nothing more than the distance from the boltface to the datum point (about halfway up the shoulder) of the chamber. You can take a once fired brass and measure it, add about .001" and you'll know pretty close what your headspace is. If you are over resizing your brass and pushing their shoulders back several thousandths or even a couple hundredths, you have headspace issues that are not due to your chamber, they would be due to your sizing.
Here is a good article on headspace
I've never had a rifle that changed it's headspace over time, not saying it couldn't happen, but I haven't personally seen it.