OP - I just noticed that you have a lot of diagnoses.

^Epilepsy {1993} ^ADHD {c. 1998} ^ASD {2000} ^GAD {2003} ^OCD {2003} ^MDD {2009} ^PTSD {2011}

Not that it IS the case, but it MIGHT be the case, that a combination of depression and anxiety leads you to settle into this comfortable and reassuring mode of wearing the same type of sweats you wore when you were 8. Maybe you are not taking any risks with clothing and not experimenting with anything new due to continuous low grade depression coupled with persistent anxiety. In other words, the comfortable clothing might be your security blanket, using an American expression.

again - this is just an idea that seems worth exploring as a "might this be the case?"