Yeah, but check to see that there's nothing calling the routine to damage you right after you "hit" an enemy, either via a switch or something else. Also, if you use different attacks or something, does it ALWAYS damage you as well, or only if you use a certain thing (like a sword stab and a bomb or something).

My suggestion: At the beginning of the routine you call to damage the enemy, do a quick <>Message:"I AM DEALING DAMAGE" and at the beginning of the routine to damage you, put another <>Message. That'll help you track down whether it's being called or if it's something in the Enemy Damaging section that's affecting you accidentally.

And for your sake I hope it's not as simple as a messed up copy/paste that still has you losing HP instead of the enemy, since those are horribly frustrating when they happen to you