Alright so me and my girlfriend are both teenagers and have been together for 3 months soon. We've bonded really well and there's no doubt we're really happy together. Since we got together we've made a lot of physical contact, kissed, cuddled and also both given each other oral sex - we've also got each other off manually.
However there is a slight problem. She is now on her pill, has been for a few weeks, and we decided to buy a pack of condoms for one evening she was staying over mine, with a free house. We did so and we got a pack of ultra-thin ones. The problem is, as soon as we're about to have sex and about to put the condom on, I begin to lose my erection even though we're both naked and in the dark. We tried twice, once that evening before bed after a few hours of lying in bed making out, and once the next day in the afternoon. Both times I was unable to get it up and keep it up.
I don't have this problem during masturbation (with or without porn), with her while making out or oral sex/a hand job and there is no doubt that she really turns me on with or without clothes. She moans, talks dirty and I tried fingering her, giving her oral sex and also letting her rub my penis during the build up to putting the condom on and as soon as it was on. She also tried putting it on directly after a blowjob...
But the end result is always the same - I'm unable to keep it up even though I find her extremely sexy and I'm turned on by her. Not to mention the fact its fine when we're just making out or even when I'm thinking of her. I'm able to masturbate without porn (thinking of her) so its not like that is the issue, its obviously me which she finds hard to believe even though both times we gave up, she jerked me off with her hands right after.
I have browsed several websites, the main thing seems to be anxiety and worrying about your performance. Being honest I've never worried about it and I have been really excited about this for a long time. I am confident in myself and I'm not exactly worried about my body (although maybe I should try and leave clothes on the first time to make sure?). So I don't think this is the problem.
Could it possibly be we make out so much in advance that when it comes to it I'm out of energy or blood from having an erection for so long before hand? If we did it straight away without cuddling in bed first (of course not avoiding foreplay) could that be a better idea? Or maybe I have watched too much porn in the past and I'm simply used to relaxing and doing it with my hands. I should say the first time we tried, I hadn't masturbated for 3-4 days, so its not like I wasn't excited.
Any advice is appreciated, I'm not entirely sure what to do about this. We've talked about not using a condom as she's well into her birth control pills and we're definitely not sleeping with others as we're both virgins at this point, she only started taking the pill 3 weeks ago, so. Whether or not that will make a difference I don't know, as it seems to be a mental issue not the actual condom.