Trying to think of something that could provide a real change for you physiologically and mentally, OP, and I thought of exercise.
Yes, I know, that old chestnut trotted out to us who struggle with low mood/anxiety/depression, etc., but I am thinking not of "go for a walk", but something regular and known to boost confidence, mood, endorphins, physical health and more - something like a martial art, kick boxing, judo, karate. Having something like that regularly in your life can absolutely be a game changer.
I thought of it when I read what you said about "it must be something I'm doing or projecting". It made me wonder if one of the difficulties for you is that you've had this feeling of sadness and disconnection for so long, that it has become kind of the foundation from which everything else is done/felt/expressed. This could definitely make it harder for you to connect, feel loved, feel free and confident to express yourself, and so on. That's what I thought of a regular form of exercise, particularly martial arts, which is renowned for creating confidence and inner contentment.
Other people have suggested forms of creativity, which I also think could be very beneficial potentially. I think you need something or a few things which you find joy in that are just yours, that improve your skills and health, and give you a real solid basis of confidence and fulfillment, which would then ripple out into your life further. You deserve to enjoy your life, OP.