Gosh, the heading of your post does not match the rest. I'm sorry that this is happening and making you so upset! To me, this sounds to be a physical problem rather than he is not attracted to you. That's a sensitive area to have a major injury and a lot of sex is, of course, mental and he perhaps has a bit of a mental block to thinking of this area (his penis) fully functioning again. He may have PTSD after the accident. I had a bad car accident and it took me years to get over the sound of breaking glass and crunching metal in my head. It's very traumatic to be in such an accident. He could probably benefit from a therapist. He literally may be afraid to be fully sexual again. That's not personal, that's psychological.
That you don't sleep in bed together though is unfortunate. That's a sign that closeness in general is really suffering. My suggestion is to plan a 'date' with him that you do NOT have sex in mind at the end of it. Just intimacy. So, do something nice together and simply hold his hand, give him a hug, a kiss, etc. Rub his shoulders. With NO expectation of sex. Just to try to build the closeness again. I would work on that before trying to have sex. He may feel you don't fully understand what he has been through and is still dealing with after the accident.
Yes, in a perfect world he'd have pleasured you in a different way while recuperating. But if you two aren't even close enough currently to sleep together, that would have been awkward. That closeness often has to come before sex when in a committed relationship. And I feel for you too because you have your needs! So, try to reconnect in terms of emotional intimacy and if you can't, I guess you will have a hard decision to make. If living in a sexless relationship is not acceptable to you and it's not showing signs of improving, you'll have to let him go. hugs
When it gets down to arguing over paying for a Viagra prescription, it's not the prescription that is the problem. I don't know if he is afraid of pain, or afraid of you, or mad at you, or over the relationship. You don't know either. All you can do is ask and not seem judgmental. I guess if you are fighting it's possible that you aren't seeming sympathetic, complaining about where's yours when he has had a couple of surgeries. You two need to see a counselor and see if there is still a reason you are engaged.