Not sure if there is anything you can do to help, unfortunately. This is an issue he has to handle, if it is going to be handled at all. While it is deeply personal and probably embarrassing to talk about, you are supposed to be intimate partners. Months without sex is a problem. If there is a reason for it, you should be able to discuss it. You should also be able to discuss if there's anything he would like to try, or if there is anything he has actually tried so far.

While it feels and sounds shitty, the inability (or unwillingness) to perform sexually was a valid reason for annulling marriages back in the days before women could vote. You two aren't even married.