Worried for my boyfriends sake

My boyfriend, early twenties, has been having some sexual issues the past few months. It isn't that he doesn't get excited sexually, but rather in the midst of it, he loses his erection. This beyond anything frustrates him. It doesn't happen all the time, or on any consistent basis. He is a smoker, as am I, and has in the past month quit smoking weed. He doesn't drink alcohol or consume anything illegal thereof. It is frustrating for me, but the main thing I'm concerned about is if there is an underlying medical problem here. He also doesn't eat too much food because he gets up for work and has a Monster energy drink, and eats a big dinner after he is home from work. He shared with me in confidence that a bowel movement only once a week or so is 'normal' for him. He has constant back pains and acid reflux symptoms. A few years back he had surgery on his back to remove hair follicles that were growing inward and causing blood to clot under the skin. I am worried that something is wrong beyond symptoms of stress. I want him to go to a doctor, but since they botched his surgery (healed incorrectly and still hurts) he is reluctant to go. I'm wondering if anyone has any insight into this matter, and possibly how to assure him that a doctor visit might be the best option. He is also worried that these problems are a sign of something worse. Any advice would be greatly appreciated.

[solace21]

Hi,
    Appears his problems are stress related. He should practice some deep breathing exercises and meditation to cool himself down. Try to relax and enjoy life during week ends.  
His eating habits and once in a week bowel movements are definite problem areas for future. He should take normal balanced food, find some time for regular exercise and ensure daily bowel movement. If still problem continues, should consult a good physician.
Solace