1999 Toyota Corolla oil leaking all over engine

Help please, I've had my toyota in the shop a couple of times with this different answer each time and alot of money later I broke down again with it. The engine oil suddenly leaked out all over the engine compartment and flooded out my altenator, the garage replaced the altenator and the valve cover gasket which they said was bad and that was also why I had oil backing up into where the spark plug sets. Got the car back and 2 days later the same thing oil everywhere flooded altenator this time they said the oil pan was not tightened down, why they had that off I don't know. Well the car was okay for about 2 weeks and geuss what it happened again. Now this time it happened while going down the highway and in an attempt to get off the highway to avoid tow charges I believe I may have damaged the engine because it was clucking away for lack of oil when I tried to start it. I didnt crank it long it wont start because of the altenator I imagine. What would cause this sudden leakage?