Thinking of you and the Boy, Teppy. (And I can relate to the conflict over feeling selfish and not wanting to inflict your own needs on someone who has far too much else going on.)
For the shorter people among us, the shoulder strap on those tends to dig into the neck and chin rather than going across the shoulder.
I've been meaning to get something like this to help with that. Car journeys are uncomfortable for me anyway - this would help with one problem there! But I always, always wear a seatbelt. Back or front seat. I've had a couple of small accidents that could have been major ones without a seatbelt.
Insent, Andi.