The best advice for people who are going through this is TO LEAVE THE RELATIONSHIP. RUN!!!
It may be blunt, hard to swallow, etc., but in the long term health of yourself, it is by far the best advice you can take. The partner with the problem is the one who has to deal with it, and as painful as it may be to you to abadon him, it is the only solution you have to resume a normal life. You need to rebuild your self esteem, self respect and awareness of your own sexuality and sexual appeal. The partner is doing lasting and intense psychological damage to your psyche. There is no amount of time, reassurance, patience, etc., that can cure them. They have to go to therapy and deal with it themselves. And the older they are, the more likely it is that it will take years and years of therapy. Sad but true. I am not proud to tell anyone to abandon their mate, but this is a serious problem that affects you more than you know.
Good luck, and remember, in situations like this, you have to look out for yourself!