For starters the two things you'll hear over and over . . . if you think you've used enough lube, DOUBLE IT. And you may want to stick with a thicker type like KY for now. Doctors use it for a reason.
Secondly, go very slow, both in AND OUT until you're more used to the sensations. You may want to try the smallest butt plug available, about the size of a thick finger, SLOWLY insert with a lot of lube and leave it in for awhile while you lie down and relax. Hopefully your muscles will do so as well.
If this still doesn't help you may have to resign yourself to the fact anal may not be for you. Some people simply can't overcome the problems you're experiencing. If that's the case practice being a good top . . . . they're always in demand. LOL
