Parenting advice for a big sister

Hey guys! So it's a big sister again needing some parenting advice. I have custody of my 14 year old brother. He has been through a lot and I'm all he has because our mom is shit and his dad is in another country. He wears goodnites to be because he were the bed and urine irritates his sensitive skin. He's been peeing through them lately. I know some people on here told me to try adult depends but before doing that I decided to take my aunt advice and try baby pants (plastic pants that go over his pull up). It worked last night and he didn't pee through but he got even more upset with the baby pants. He actually started crying which startled me because he never cried when he had to wear goodnites. I'm in the process of getting him medicaid so I can get him a therapist but in the mean time I may have to look for one to pay out of pocket. I'll probably have to break into my savings but he needs therapy. I feel like I'm not doing a good job I guess.... I'm 26 so obviously I know nothing about raising a teenager. I'll take any advice I can get because I don't want him to be sad. I want him to be as comfortable as possible. He's my little brother after all! So any parenting advice to help him through this would be appreciated!