You are ungrateful yes! Your husband is doing his best and taking on the majority of household tasks, school runs, plus has been transporting you to appointments and this is still not enough for you!
Imagine if the roles were reversed, and the wife was the only one working, doing all school runs and the DH still wanted to be driven to group sessions during her working day! He would certainly have his ass handed to him!
Perhaps the guy is just exhausted and feeling fed up of balancing everything in addition to also working full time while you ask for more and more of him!
Sometimes people who are Ill become very selfish and can't consider other people's needs or the impact of caring for them on another person to the extent they become a burden due to their own selfish attitudes
Perhaps he didn't expect to become your long term 'carer', if he begins to seek comfort and support outside of this relationship, he will be blamed, so instead of wineing about how you would get to the appointment, put some practical plans in place as any reasonable adult would do!
If DH suddenly chose to leave you or God forbid became incapacitated himself, would you not find a way to get to your appointments if they are so important to you?
Kind and patient People get tired and fed up at times, you seem very selfish and centred, we get it you have an injury....but you are not the only one in your relationship that matters, on a daily basis how do you practically or emotionally 'show up' for him? When did you last acknowledge or thank him for the support given to you at this time
Keep this up and you may find yourself dealing with a lot more practical tasks alone, if my husband behaved in this way, he would be called a lot more than 'ungrateful' and I would be gradually telling him that I was unwilling to take any time off during my working day to transport him to appointments or use my leave to taxi him around