Sudden urge to lick a woman's or a girl's ass. so much that.

It is pretty normal to think that, but in my opinion it's kinda gross

It is very normal, the woman who taught me about sex was older than me by about 30 years, she loved to have her ass licked. When I got older I would explore women's asses in sex while licking their pussies. Some were OK with it other's preferred me not to do it again. I knew one that just would flip as I licked her ass and reach around and pulled her cheeks apart so I could get full access to her rosebud. My female partner loves it, she enjoys me twirling around her ass. When a woman gets my attention I do wonder about how her ass looks and would taste?

For sure. Would lick my SO's anytime. But only get to do it now and again.

Trust me everyone has fucked up sexual fantasies.

Just do it

All of those things work for me with exception of the diapers. All are very hot. Whatever rings your chimes my friends.

It seems normal to me. Everyone has a different urge. This one probably shows that you and I are both submissive. I have fantasies of submitting to a woman, ending in licking her ass and cumming in my pants while I do it.
Other submissive things are even licking pussy, sniffing panties and wearing diapers. Have you thought of those ideas?