I understand your sense of confusion!
It seems you have been very patient and considerate with his needs.
We all need some time and space to sort ourselves out at times. Our best friends will allow us this time.
There comes a time, though, when it's also important to address this, with sensitivity to whatever he is experiencing; yet, also very directly. Hopefully, he can talk openly with you and hopefully he has some understanding of what is going on for him. If he cannot talk with you and/or is also confused by this, please encourage him to see an MD for a physical evaluation. He may or may not also need a psychological consult/therapy, depending upon root causes of his issues.
Please be warned that many guys do not want to tell a doctor or anyone at all, that they are experiencing difficulties of this nature! It may be extra difficult to get him to agree to seek assistance in sorting this out.
You may find out he may be very comfortable without sexual activity.
If so, you may need to decide if his style is a good match for your style and meets your needs.
Best wishes and Happiness to Each of You!