Is my fetish normal ?

For a girl, it is as normal as eating food and magically having it come out your ass 12-24 hours later; looking somewhat different and compacted.
It does not however mean you are bad and want a stranger to violate you. I guarantee you are normal. I suggest you and your BF try role play, making sure ground rules are understood and you each understand an agreed safe word.
Have fun... If you do this with mutual respect, I'm sure you will have lots.

technically it's not rape if you're willing.

but seriously, hey some people like roleplay. perfectly normal - just be sure he respects your code word.

If a women asks me I don't mind at all. Can be funny and very exciting but I need to be in the mood for that, of course.

It's completely normal to have fantasies like that. I've had similar fantasies myself and role played them out with both of my lovers.