Your partner will already know that as well as not being able to achieve a decent erection, it is nigh-on impossible to have an orgasm. Strangely enough, he may not actually have linked this as a side effect of the medication, as the list of side effects contained within the packet may refer to this as 'sexual disfunction,' which does not give a good explanation. He may just think that he has lost his sex drive or feel a failure as a man. It is very important that you talk about this with him. OK, he's a sensitive soul but he may also be suffering needlessly with thought of not being able to perform!
As far as I know, after trawling through websites (a couple of years ago mind) if you live in the USA, Dr's will give you a medication to counteract this unpleasant side effect. If you are in the UK - hmmmm!
A good website is www.mercola.com. This guy has remedies for all life's little problems and has a fabulous section on anti depressants.
I hope you find this helpful tiger and I really sympathise with your man....and you, if you ain't getting the good lovin'
you deserve!