Drywall tape cracking, floor boards uneven?

I have lived in my house for almost 4 years now. Over the course of the years the drywall tape in my house have started coming loose from the drywall. It creates hairline cracks. In the past year it has progressively gotten worse and worse and seems to be happening more often through the rest of the house. Most recently, I've also started noticing my floors suddenly are becoming uneven (starting to bulge in some areas or shrink in others). Some of the ends of my walls or wood beams (that have drywall over them) are buckling in a little bit. It almost seems like they are forming a u with the top parts of the u being the very edges of the wall/boards. My only guesses are that the issue is either moisture or foundation problem. I don't see any cracks in my foundation and all cracks are vertical (though I do get some horizontal bulges) and appears to only happen where two pieces of the drywall meet and are taped together. Is this a humidity problem? Does anyone know who I would contact to diagnose this and fix it? I had a couple general contracts out and asked them and they were like it just happens with no explanation. I understand things like settling can cause this, but I imagine settling is gradual overtime and not just suddenly there. Side notes: I live in a town home in a community that is 20 years old. I am an end unit. My neighbors' houses have none of these problems so I doubt it is build quality. My home was a foreclosure in a pretty decent condition when I bought it 4 years ago. I have been running my Central Air/Heating a bit more in the past year which has me leaning towards humidity issues. Any help on what the problem is or who to contact for more information will greatly be appreciated!