What was your original problem? Was the clutch starting to slip or was it getting hard to engage the gears? Sounds like you could still have some air in the system. Could also be due to worn master or slave cylinder seals. Look for signs of any leaks if the fluid level is dropping. Your mechanic should have spotted any slave cylinder problems but the master cylinder may be starting to go. Check under the dash behind the firewall. Here's a sort of silly reason but I've also had my carpet covering kit slip forward and get under the clutch peddle preventing it from going down enough to release completely.