problem with erection???

when shes preforming oral sex on me..its at its peak..when i go to incourse it loses its peak real fast..so i dont understand..im on meds im 46 yrs old..buty the oral part that she performs  is erect..just until its time to have sex..she says mabey  ur not into it..thats not it cuz i am...please help me?????????????

[Super33]

Maybe it happened the first time for some unrelated reason.  After that you became afraid of it happening again so you're mentally causing it, expecting it to happen so you're actually making it happen.  

Maybe you're affraid of her becoming pregnant....  

[mightyhealthy]

i have this problem too, although i am 18 years old and i should be fully functioning.
i believe it is any distraction, if you use a condom, taking time to open it and put it on your penis can distract you and it can go down. you could try some P.C muscle exercises, this is the muscle that controlls your bladder, you can feel it between your anus and your penis, try to tense your penis and you can feel it contracting.  find p.c muscle exercises online! it has started to work for me so i hope it works for you! :)