Speaker not working as it should be.

I had my screen replaced a few months ago and have had some intermittent issues that I can deal with. About 3 weeks ago the speaker has become very weak, I can barely hear it even when I switch to speaker phone and turn the volume all the way up. When I plug into the aux port everything is fine but I cannot use speaker phone without having to hold it to my ear. Any one know what would cause this?