She won’t stop peeing!

Hello everyone, I have a 7 month old medium hair black kitty who’s still having some litter box issues. She uses it through the day (to my knowledge) but once we get ready for bed almost every night she pees on the bed. I’ve discussed it with the vet and he keeps giving me deadens answers. We’ve gotten a second litter box, a litter that she seems to prefer, and enzyme clean everything that she pees on and it’s still happening. I don’t know if it’s litter box aversion or something like that but she only pees on things that we sleep on. This has been an ongoing struggle for months now and I seriously don’t know what to do anymore. If anyone could please reach out and help, it would be greatly appreciated. She is spayed and is missing her back right leg. She’s desperate to be outside but because of her leg and our living situation, outside roaming is not an option.