I very much doubt its you. The reason i'm saying that is i did have similar issues and no longer have any problems. My gf has not done anything to change her appearance. The only thing she did was make me over a period of time feel more relaxed, less stressed, less anxious.
She very gently said stuff to get my confidence back up. I did need my gf to broach the subject as i was embarassed and getting frustrated at times.
She was worried that it was her so it did not help with her confidence but time and talking sorted it out.
Its a loop. man feels anxious, therefore has problems. Next time he will be thinking about previous performance and get more anxious. More Pressure!!
Askaquestion He must fancy you, find you attractive, like being with you. Otherwise why has he declared his love for you already
. Unless you smell, shout stuff out that he finds off putting like "whose your mummy big boy" (appreciate some men may like that but not all), have said something along the lines of "its not very big is it?) then it does suggest to me psychological. I am not a doctor. Men don't like to discuss as it suggest a lack of masculinity. This is very common as men get older.
And he will probably respect the fact that you want him to be as turned on as you if you bring issue up in conversation.
If you are not sure how to broach then you could mention a friend had a partner with similar problems and he got stressed but by talking about it took the stress away and after a period of time were sorted. You could mention the things that was making that "made up person" stressed (stress from previous break up, stress from work, stress from friends, stress from children, stress from being unfit).
The key thing is to ensure that at no point either of you expect that next time it will be sorted. As that just puts pressure on the next time.
As a last question i am not sure if you are using contraception or not but could he be stressed about making you pregnant?