1993 Toyota Celica new clutch slipping

Hi, my name is Evan. I bought this car with 112,000 miles on it. The clutch slipped so I got it cheaper. It slipped intermittently. It would slip for about a weeks period, then for about one day it would lock up fully. I replaced the slave cylinder and bled it completely. It still slipped intermittently. So I had the release bearing, disc and pressure plate replaced proffessionally with a new engine as well. It still slipped intermittently. The mechanic SAID he resufaced the flywheel. But I dont believe him. So I replaced the master cylinder and bled it again, this time bleeding an entire 2 bottles of CLEAN brake fluid through. Meaning after I bled all the dirty fluid out, I continued bleeding. It was so clear that I thought it looked like air coming out of the bleeder valve. This worked for about 3 days, then it started slipping again. This was about 6 months ago. It still hooks up about one day every couple of weeks. Do you think air is gettting into the system still? Can a few air bubbles cause it to slip or can a worn flywheel cause intermittent slips? Tranny problem? Im extremely confused please help! Thanks, Evan