2000 Honda Prelude Car is losing oil/smoking

I have a 2000 prelude with 73000 miles, 5speed. I noticed my cars exhaust tips started turning black. My friend was driving behind me and noticed when i stop and take off my car blows black smoke. I check my oil level frequently and always end up having to add more oil to get to the full mark. I've checked the engine bay for leaks, and the driveway and have not seen any oil leaks/spills. I have added a fuel injector cleaner but am pretty sure that did not resolve the problem. The only thing i can think about changing is the pvc vavle. Please Help. Thx.