Is my Guinea Pig sick?

My guinea pig has been seeming a little under the weather. He appears to be eating normally (and drinking, but maybe not as much?) and will still get excited and affectionate and everything like usual...but I'm concerned about him because he's been wheezing quite a bit accompanied with coughing or sneezing. He's also sometimes very warm to the touch, but I'm not sure if it's because he's been huddled up in his bed with his stuffed animal keeping warm on purpose or not. It's been on and off for a little over two weeks, and some days he'll do it and some days he wont. There is no crust around his eyes or nose, and he seems otherwise healthy. I've been keeping his cage as clean as possible and he's been getting fresh food, hay, fruits, and veggies daily as per usual. Money is kind of tight, so I didn't want to pay for a vet visit if I can help it...but does this seem like something that I need to take him in for? Is there anything I can do to help him "get well" without taking him in? Or is it allergies, maybe? (All of the humans around me have been suffering from allergies really badly lately...I was thinking maybe my piggie is having the same problem?) Does anyone know? He's been misbehaving a bit lately and I was wondering also if maybe he's trying to indicate to me that he's not feeling well and wants me to help? I don't know...