Is he comparing things to the way they were when you two first met? Because the high, bubbly stage of infatuation doesn't stick around; long term, what lasts is more of a warmer, calmer love. Maybe he's one of those guys who always chases the high in romance, and hasn't had many relationships that last longer than a couple of years? Or, maybe he's feeling the loss of the infatuation stage and thinks it's all lost?
Anyway, it's wonderful that he has been so supportive during a rough road for you. Talk to him about what you want with him in the long term. That might help you both get your eyes back on the prize.
My first question is are you in a place where you are feeling sexy? Like you want to do all this?
You've been through a lot, and are just now coming up for air. I don't know how spicy you are thinking, but your mental health is really important, so don't push yourself.
Why not start by just trying to show more affection? If that's something that you enjoy, do more of that. Hug him, kiss him, tell him you love him and appreciate him.
Initiate sex. I don't think you need to go all out with sexy lingerie and toys and whatnot, especially at first because that could seem forced, but just start kissing him one night - or day, however it moves you - and go from there.
Dryness is a real thing. Lube is your friend. It doesn't mean you aren't aroused by your partner, and that may be something you have to explain to him. It will happen again at some point in your life - medications, birth control, hormones, stress, age, etc., all play a role and have nothing to do with how hot you think your partner is.
If you are going to be using condoms now, make sure the lube is water based, and get one for sensitive skin. It doesn't matter if you think you have sensitive skin or not - they are usually just made with better things for women's bodies and avoid harmful things like parabens and glycerin, etc.
Here's one list, but there are many - google "best water based lubes for sensitive skin".
https://www.prevention.com/sex/g32865699/best-water-based-lubricant/
If you aren't going to be using condoms, you can try other types -
https://www.wellandgood.com/best-lubes-for-sensitive-skin/
Therapy is a great thing, but can be really tough, too. I'm glad your partner is supportive.