Over and above consultation, you may try Breathing to orgasm technique. Google breathing to orgsm to know the details. Take it as a game and not as a treatment. Study the technique and put it into practice. If she cooperates, you can try for some time. This involves three types of breathing. Alternate breathing, simultaneous breathing and circular breathing.You may talk to consultant about this method.
Both of you need counseling and face the problem with loving cooperation. It would be a long process. Both of you will need patience.
Ignore BluCrystal, you aren't being selfish by asking this question. It's probably a lot more than excessive bashing of sex that is affecting you, it's also completely normal to be turned off when you know your partner is not into sex, because if you are like most people, you are not turned on by rape.
You say you believe her but I bet you've had doubts, anyone would. You spend so much time hearing about how much she hates sex, that by the time you are about to have sex you begin to doubt if she really does like it with you, and that would be enough to scare the crap out of anyone, wondering if they are damaging their partner or possibly raping them when all you want to do is make love or have a little fun. Even if that isn't the case, you are still trying to share an intimate, passionate experience with someone that you know absolutely hates everything to do with it - that would really ruin the experience for anyone, it's a major turn off, especially if you are the type of person who really gets off on pleasing and satisfying a partner, you might be better off with someone who gets really excited and loves sex all the time, it doesn't sound like you are very compatible with her. If my boyfriend spent the whole time talking about how he hated sex, and then we tried to have sex, I wouldn't be into it at all either!
That doesn't mean you can't make it work if you really care about her or love her, but IMHO I think the right person for you (your soul mate) is supposed to be a perfect fit for you, otherwise trying to have sex with someone who isn't compatible with you is never going to make you truly happy. That's what I believe and unfortunately I think most people are just settling for partners that are not right for them, which is exactly why marriages are not lasting very long these days.
You can probably voice to her your concerns, but it's up to her to get help (if in fact this is a problem for her). You can't force her to do anything. So if I was in your shoes, I'd be making the tough decision, do I stay with her despite how much it is affecting my mental health and sexuality or do I move on and find someone who is a better fit. Because honestly, there could be a lot more there than meets the eye, perhaps she isn't even mentally unstable, perhaps she is just asexual and truly doesn't like sex, and that is not something a person can change about themselves. Sexual abuse in ones past doesn't necessarily equal someone hating sex as much as she seems to, so I wouldn't be surprised if there is more going on there, but even the fact that you know she had "bad experiences" would probably turn you off and make you feel upset or concerned about her.
I'd say it should have quite a huge psychological effect on you, because it's a completely abnormal and unhealthy situation that she is putting you through. Your girlfriend may not be healthy or mentally stable, I'm not sure what the issue is but it may need to be dealt with professionally.
You may also want to look into counselling to better deal with what is bothering you and unless you are a robot, this situation should be bothering you because it's really not healthy or fair to you.
That is a rather selfish question, don't you think? Your gf needs your SUPPORT and PATIENCE, and should be in couseling for this. She doesn't have some psychological disease you can catch like a cold. Encourage her to seek counseling, and maybe go with her. There is nothing wrong with YOU, but there IS something wrong with your attitude about it.