Orgasam with a woman who has had a hysterectomy

I have recently started having sex with a lady that has had a hysterectomy.
I do not come with her and I have never had that problem with a woman
who has not had a hysterectomy. Is it because there is nothing in there
to stimulate my penis. That is all I can thing of, everything else is the same.
See is very beautiful and very sexy, but I just can't come.
Thanks, any help out there!!![/list][/list]