I have been in two long relationships with hot hot girls. Now I am having trouble being attracted to others.?

I have been in two back to back relationships with really beautiful women. I have never had any trouble in bed ever in my life. I recently broke off my relationship of four years with the last one and have been dating again. I have been dating women who are not nearly as good looking (internet dating...). Twice in a row I have taken one of these girls home just to discover that I am struck with temporary impotence. I am so used to dating model types that regular girls aren't doing it for me. Any advice?