Why didn't he tell me he was impotent before we fell in love?

I don't know what to do, I feel I've been cheated; my boyfriend has no sex drive and is impotent.

We have only been together 8 months but he allowed me to fall in love with him before being honest with me. I feel as though I'm being selfish but I am only 53 and he is 55.

 He says it's common in men his age. I was hoping to be having a healthy sex life for at least another 30 years! He is under the doctor but seems to accept that things will not get much better.

He is everything I could ask for in every other department. It's got to the stage now that it's all I can think about and every time I mention anything it leads to a row. Help