I'm not the ultimate authority, however, I would like to share a few thoughts with you...
"I have read up that doing enemas does cause Incontinent sexually and was wondering if maybe he is doing this to better our sex life or could it be something else entirely?" I've been closely alligned to the subject of the enema for a decade, two, or three, and this is the first I've heard of "Incontinent sexually" because somebody is doing enemas.
First off, incontinent relates to being unable to retain urine or feces voluntarily... It is my thought that the word you might have been reaching for is impotent, or impotence... Being impotent, or an impotent experience, is when a male is unable to engage in sexual intercourse because of an inability to have and/or maintain an erection.
I've never heard of anyone who does enemas, 100s here, suggest that enemas can be the causation of impotence. Personally, if he is drinking as much as you stated, that could be a cause of his impotence; or, the cause of his impotence may be the reason that he is drinking so heavily.
"We hardly have sex and the times we do he is drunk and never finishes, and just recently he does not even get hard for me anymore." What does that say to you sexygurl?
I'm not a psychologist, however, I have concerns about your boyfriend's drinking.
Imho, it is my thought that your boyfriend might need some therapeutic help, and maybe even intervention. And, if he would start that process, it might be that you would benefit from tagging along, to fully understand and appreciate the dynamics of your relationship with this man.
I wish you well!
Hermann