Husband thinks I'm cheating but I'm just depressed.

I have suffered from anxiety and depression for a few years now, since the birth of our second and final child in 2015. I have tried numerous counsellors, medications and an overwhelming amount of natural remedies. While I have good periods- I just can't seem to beat it.
My partner is extremely supportive but doesn't really understand mental health because he has never suffered it. (I am currently in weekly therapy and on medication).
The past few weeks have been some of my most challenging and the kind of person I am means I internalise my struggles and withdraw, I struggle to speak to even my husband as I do not want him to feel responsible for fixing me.
He has just opened up that he is really struggling, with jealousy and feeling suspicious. I know it will be partially due to me withdrawing and a lack of effort in our sex life (though still 'letting him have it' 2-3 times a week out of guilt) but he also says he feels like I am trying to impress everyone else lately. I have always been someone who puts an effort into their appearance, even on my worst days I will usually be donning at least a little makeup and nice clothes, I feel like its a small step to feel a little more normal and not like I'm making more effort than I ever have. I have also been doing group fitness classes because my GP recommended it- plus I ended up actually enjoying it and for some reason he apparently just thinks I'm there checking out other males. He also mentioned me not wearing a bra, I have tiny breasts after children and feel like as long as my clothing isn't see-through there really isn't any need.

I'm just feeling at a loss, I don't know how to reassure him, I don't believe I'm doing anything wrong nor anything that should be making him question me- I can't think of anything worse than trying to please another male so there is absolutely nothing else going on, but at the same time mentally I just don't have anything more to give at the moment and feel like I really can't be bothered trying to convince him because I'm trying to convince myself its worth being alive.

Also what do I do next, for myself? Medication isn't helping, therapy isn't helping, lifestyle changes help short term- so what next? I don't want to kill myself but I don't want to live feeling like this any longer.