Lots of discharge after masterbating!?

The discharge is just your body's natural lubricant doing its job. Your vagina secretes fluids as you get aroused to prepare itself for penetration (which in your case doesn't happen). It lubricates the skin and prevents tearing and other injuries to the sensitive parts. When you have sex; the lubricant is usually rubbed off by the friction caused by the penis or other object, but when you don't penetrate the fluids just hang around. It's nothing to worry about and is perfectly normal.