2004 Jeep Liberty Horn

I am having a problem with my Horn. I am lost on how to fix this. My horn stopped working awhile back. I noticed right before it stopped it kept getting harder and harder to press the horn. I have checked the fuse and the relay and they both are good. The horn is good because when I lock the car the horn beeps. Just not when I press it on the steering wheel. I heard it could be the clock spring but I'm not sure about that because my cruise control and stuff works but my radio controls don't. I figured that was because I put an aftermarket radio in. I don't want to buy something pricey if that isn't the problem. This needs to be fixed as soon as possible. Any help would be great, Thanks!