hi im 17 and over the last 6 months have not had sex not because i dont want to or because i havnt had the oppurtunity, because when i do get it up i go to grab a johny or some lube, put the condom on and i can feel at the bottom of my penis that my errection is gone and fail to even get it in as it loses its hardness very fast. i have been with my girlfriend for around 4 months now and feel that it is causing tension between us and i feel bad as i cannot settle her sexual needs

before the last 6 months i had a very healthy sex life and was having sex once or twice a week and since then cant get it to stay up

i have a very tight foreskin also which means that i do need to use a condom or lubrication or it really hurts after getting say a quarter of the way up

i was told that i should get a circumcision around 2 years ago but really didnt fancy the idea of an operation on my penis but now i think that that might be the problem

any ideas or anybody had the same problem?
what should i do ?

thanks