My boyfriend gets an erection but as soin as he puts on the condom its gone. ?

"ED": Erectile dysfunction, inability to get and/or maintain an erection, is very common---much more than people like to admit. Premature ejaculation (come too early) is extremely common and this frustrates many couple. You may want him visit a doc to find out exactly why--as there are good therapies available.

Erectile dysfunction: Assuming he is a young healthy male, i suspect anxiety is a likely cause of his ed. I suspect he practice putting on condoms by himself severaly times first and masterbate as a form of exposure therapy. Seeing an md who can prescribe a viagra (sildenafil) like med might help make it more likely to last and get over the fear of failure.