Clutch Slipping

The other day I was going thru the gears when engine speed increased significantly and I could smell burnt clutch. Crawled under the car, the rod to the clutch has slight play in it so I think it's adjusted correctly. Noticed an oil drip from the flywheel cover so removed it. There was oil inside dripping from the clutch fork. Doesn't appear oil is leaking from the intake or valve covers. There is oil at the front of the engine also, but wouldn't think that would get into the bell housing?
I have to conclude that the rear main is leaking. I have oil spots on the floor but didn't think it was a huge amount.
Question is, can that be causing my clutch slippage?

Clutch Slipping