Is it normal to only be able to orgasm if my finger is inside my partners anus?

It started to be a problem lately that I can only reach orgasm if atleast one of my fingers is inside my partners anus. This used to be fine because I would just slip it in during intercourse but now intercourse is less frequent and I have to satisfy my self often while my partner is relaxing or sleeping beside me but for me tm orgasm I need to pop a digit inside. This usually wakes my partner up even with good lube unless there has been a lot of alcohol taken and that usually causes a row. When my partner is just watching t.v. or something it's fine but I wish I didn't have to do this . Is it normal to get used to something during sex and without that particular thing orgasm is basically impossible?