It certainly sounds like your relationship has some issues - having ANYONE call you a loser is unpleasant, but coming from your wife it is especially hurtful.
From what you've said, however, I don't see any reason why you should suspect that your wife is lesbian. If, for example, she seemed overly interested in her female friends - enjoyed touching them, for example - then I would be slightly suspicious. Instead, it sounds more like your wife simply has lost interest in sex in general. Which isn't uncommon, particularly in women who get little physical satisfaction from the act of intercourse.
It's GREAT that she has been honest with you about her not achieving orgasms with you, although I'm sure it was hard to hear. Many women simply keep this fact quiet from their partners, so her feelings comfortable enough with you to share this was a big step. The important thing is for you to understand HER position - she is a woman who has already had children, who has been married for 38 years, who has never been sexually satisfied, etc. Undoubtedly she is feeling frustrated and possibly upset with her position in life.
The best way to "win her back" is to be empathetic. Do not act judgmental, and do not be angry with her. Instead, try to romance her, and be kind. Try taking her out for date nights - go to a romantic restruant where both of you have the opportunity to dress nicely. Surprise her with flowers or a bubble bath. Or, you can try giving her space. Ask her if she would like to go on a weekend trip alone, maybe to a spa.
As for the sexual aspect of your relationship: if you want her to become interested in sex, you need to show her that the activity will be based around her and her pleasure. Ask her, if you haven't, whether she has ever had an orgasm with another man - or through masturbation. If she has, ask her what was different about these occassions. Was the touch different from what you use? Were toys involved?
If she has never used sexual toys before, you might want to buy her something simple and non threatening. There are many wonderful vibrators on the market, go to GoodVibrations.com for examples. Ask her if she would like you to use it on her - or, instead, simply give her a chance to get used to the toy on her own.
As for oral sex - MANY women do not feel comfortable with this act. They may feel self conscious, or it simply may not feel so good. Ask her what it is about the act that she doesn't like. See if maybe she would feel more comfortable if you preformed the act while in the shower with her, or immediately following a bath. Make sure she understands that you ENJOY the act, and expect nothing in return.
My final piece of advice is pornography. This might seem strange, but your wife may benefit from watching pornography before or during the actual sexual act. Women can be just as visual as men, and having this extra stimulus may be a real benefit. If she is someone who is against pornography, or who has never seen it before, it would be a good idea to introduce this idea casually. There are many top quality pornography videos that are non-sexist and geared towards the female viewer. Check out GoodVibrations.com for examples.
If you have any questions, feel free to ask!