It will be ideal if you can consult sex therapist.If consultation is not possible , visit Wikipedia and search for premature ejaculation. other alternatives are as under;
kegel exercise for both.
Male deer exercise and female deer exercise
Sat kriya
spina rotation.
Sexual reflexology.
Gradual exposure to each sexual activity.; In this ,keep your goals lower, do not plan for orgasm. You will find details of this sex therapy in some website.As both of you are cooperative to each other and determined to solve the problem, you will succeed in your attempt. If your are yoga oriented, you may learn kundalini yoga.By pranayam, (controlling breathing) you can control your sexual arousal. Deep and slow breathing, gives a trenendous control on you sexual urge.
Thanks for the response Jary, anyone else?
Hello I'm sorry to hear of your problems. First of all its brilliant that the two of you have remained supportive of the other. I can't imagine how frustrating it must be.
I think you may need to see a sexual health specialist as they would most likely be able to help. As for your gf, has she tried using sex toys? It might not be what she wants but using sex toys might help her find it easier. I know you said she's well lubricated but it might even help to get some extra.
I think the priority tho is getting you to see someone about losing your erections. I wish I could offer more help because you both must be at your wits end.
I'll keep my fingers crossed for you that you find a solution!
Best of luck