This is my advice for you. I feel what your going through exactly, and although I can't tell you if this will work for sure, I can tell you that it probably will work, and I ca give you an update in a month or so because I'm in a long distance relationship so I havn't had sex since the same problems that happened to you happened to me.
At first we just started dating, so I didn't totally feel safe with her (trust, her thoughts, etc...) We had sex many times but I couldnt cum. I came once from doing it myself after sex, I tried to do it myself on 3 other occasions after sex and I still couldnt come. While having sex with her, I was only thinking about her, and if she was enjopying it, if she was happy, if my dick was good enough, if I was good enough, whats in her mind, etc... She even told me to just relax and stop trying to be better everytime and that its all in my mind. Because of my past, I have a fucked up mind, so I always think about stuff. When I go to see her soon, Im very confident none of this will happen again. I feel safe with her, I trust her, and most importantly I'm working on my mind. So, in conclusion, I'm 100% sure that its all in your mind. Just enjoy.
Now, more information that may help. There have been comments taht you should stop masturbation, but that infact effects the mind alot. It didnt work for me. Before going to see her I didnt masturbate for 2 whole months, and after having sex with her I still couldnt come, so stopping masturbation is not the answer. You may ask why not? Well, because you are telling yourself I need to stop masturbating in order to come, so infact you are worried about not being able to come when your with her, and your sort of preparing yourself for sex, which you shouldnt do, its not a game, its not a battle, its fun. Don't think about sex, dont prepare yourself for it, just go do it and have fun. So by stopping masturbation I dont think you will help yourself, because the mind is the strongest sex organ. I didnt masturbate for 2 months, and after much much sex, still no orgasm. I would continue life as it is, but if you do masturbate, maybe not as much, and differant methods. I just masturbated 3 times before writing this post, each time with a condom on, each time to my GF's picture, the 1st time I had a medium grip, the 2nd time (10 minutes after) I had a very loise grip and the 3rd time (an hour after) I had a very loose grip again. Each time I orgasmed. Why? Because of my mind. I was enjoying myself, it took no longer than 10 minutes to orgasm to my GF pictures with a LOOSE grip. I can't stress enough how loose this grip was, I can only say that it felt like throwing a sausage through a hallway. Now, more important info, you may want to begin working out if you havnt (I do every single day), and eat healthy, more importantly things that are good for sex. Eat asparagus, just trust me on this one. Also, if you want take a pill of zinc everyday, I do once a day, but this isnt a MUST. So, the steps I've taken I have told you (healthy foods (sex foods), masturbate with a loose grip with a condom on, clear your mind, excersise, don't think about it; enjoy life).
I hope I helped. I was sceptical about posting at first since I'm no expert, but I remember a while back I asked the same question as you and would hav eloved any sort of reply. I hope all goes well with your girlfriend. Just don't think about it, the more you do the more it will hurt you. When you have sex, tell yourself in your brain, or even better talk to your girlfriend while your fucking her and say "Im going to fuck you for so long, I dont want to come, please I hope I dont come". You are telling yourself to come that its nto going to happen. Its the same as telling your dick to get hard, its not going to happen. Let everything happen naturally. After experiencing the same thing, I went to a doctor asap, he said my body is perfectly healthy, I'm not low on anything, my blood is fine, everything is fine. He only told me I lacked some Vitamin D which wasnt serious (we get it from the sun), I take 1 pill a day now of Vitamin D, but this doesnt ahve to do with the sex. He suggested to me that its all in the mind, Im forcing myself to come and its not happening, and that I should ease up on masturbating. He told me nto to think about it and just let everything be. When you are having sex, dont try to force an orgasm, I tried several times and I pissed, although it felt good, but it was piss! If you have any questions, just ask, but the main points are: continue life as it is, eat healthy stay healthy, dont think about it, its all in the mind, dont be scared. Take care and Good luck! I'm in the same boat as you, I mean its good to make your GF come 3 times, and hear her say noones made her come like you have, but I know what your talking about in regards to the confidence part and just akwardness, beleive me. I'm going to be fucking all day every day next month, and I know Im going to come, but I don't even want to come!!! Peace.