rear shock
 

I think my shock has lost compression or what ever ever the correct term would be. Its there a way to repress it or refill the gas chamber. If so what kind of business can do this? Regular bike shop or shock specialists.

Maybe just needs a new valve. A suspension shop will do a rebuild on it. Maybe price out a replacement though?

just find a shop that will rebuild it. and while youre at it you might as well have them revalve and/or respring it for your weight.