It took me nearly 5 years to have an organism with my husband. It was just hard to get used to his rhythms. I never worried about it and just went with the flow.
Uhm.... I'm just a regular guy and do not have a degree in anything to be confused with the medicinal trades, so I won't pretend to be. I also won't run the "red flag" route, at least not yet.
Since I know nothing about the situation, except for what you've noted above, I'll respond with some situational information from my life and those of friends.
About not getting his, there could me many, many reasons he cannot achieve an orgasm. Medical issues come to mind as well as mental conditions. Medically, I know of nobody personally who cannot achieve an orgasm from "being fixed". Maybe there is a chance, but I know a few guys who've had a vasectomy and none of them complain of issues.... not a one.
Mentally.... there was a time when I was concerned if I was "really" doing it for my wife. At the time, I also suffered from clinical depression and sometimes could not "get mine" regardless of what we did. (Mind you, this was maybe 4-5 times in 20 years, but in about a 2-3 year period.) I've often worried about being the "2 pump chump", as we used to worry about in our younger years. (The male ego does weird things to us.)
If I were you, I'd not worry about it so much, but would suggest to him that he see his doctor regarding the issue. One could sit and hypothesize about any number of would be causes, but really... what is the use? The way to address this and any problem is directly.... his issue/not so much yours, and his doctor is the best starting point.
There are so many things in your post that raise red flags.
Why is he "fixed", as you say? You're 29, is he also the same age?
A man who isn't too shy to get naked and have sex with you, but IS too shy to have an orgasm . . . I bet he's got a lot of other oddities you haven't discovered yet.
He either "can't" or he's telling the truth and he "won't", and I don't know which is worse for the relationship.