Is it normal for my wife to try to destroy or deform my penis?

Im just curious and cant understand why she does this all the time. For the most part I don't mind but sometimes she takes it over the top and will go to the point where I hurt for days after. It seems the more I hurt the more she gets turned on and gets mad when I ask her stop.

It started with a nibble once in a while but has developed in to some what of a concern.

Even sometimes during sex she will make me pull out so she can bite it. Shes never drawn blood, but isn't satisfied if there not at least a few teeth marks.

Is she worried im cheating and feels the need to leave her mark? She doesn't bite me any where else or leave hickeys
just bites my dick.

I have even tried to return the favor and bite her breasts or her vag but she gets mad and tells me it hurts.

Lately she has really started pushing a new favorite of hers where she busts out the heels and steps on it. Again something I don't mind once in a while but it can get really painful. I cant seem to remember a last time we had sex where she hasn't tried to leave me in complete agony.

Is this normal?

I tried to explain to her that she has a fetish but she took real offense to it. She said it made her feel like a sicko.

Why is she doing this? Is there a way to try and incorporate some gentler foreplay once in a while? Im not sure if my penis can take much more of this and im worried it might lead to ED somewhere down the road.