All I really asked was .. Did he kiss your buttock prior to your marriage or was this something he just started to do out of the blue once you were married and it was a shock to you..
There are many women that have married a man and then he suddenly acts different... and it can be scarey for some women when a person suddenly starts doing something new and it feels odd.
If you are okay with him kissing you this way , then good ! Enjoy having a husband that shows affection in that way.