(Texas) Power of attorney seems fishy? : legaladvice

So, I'm 29 and my parents don't allow me to get a job or move out on my own and every time I try to, they threaten me with this. I do have mental disabilities, however I am fully functional and I also have never been diagnosed. This leads me to questioning the veracity of my parent's threats. I do remember my parents dragging me into an SSA office when I was younger and they made me sign some document without me reading it. They just told me to sign it without question and being my parents I didn't think to question them. Later they told me that I had signed away my rights (their phrasing) and that they now have power over me. Every time I try to run away they also threaten to call the cops and they tell me that since I'm disabled and I have no guardianship over myself, whoever I go to can be charged with kidnapping since my parents didn't consent. I'm also not allowed to have friends or anything because they use this to dictate my every move. They tell me I'm crazy and helpless and I can't be trusted and that's why for my own good they got this thing.

Other things that might be important that make my question things:

They don't care about my well being. They don't allow me to go to therapy even when I've asked. They refuse to allow me to see a doctor and when I finally did, they threw away my medication because they claim it was bad for me. I know for sure I do have a mental disability, I just don't know what and once again, they've never took me to get diagnosed let alone therapy. They've always been controlling and I wonder if this is just another method. I get too scared to call Suicide Hotline when I'm depressed because they had me convinced for the longest time that, quote, "they'll lock you up in a mental asylum for life and take away your phone and never let you talk to the people you love ever again and they'll treat you like you're crazy." I've since learned this is obviously not true, but it's ingrained in me now and I have a hard time seeking help. I feel that this is also yet another form of control.

Anyways, how do I go about verifying if they really do have this thing over me? What are their rights if this is true? What are my rights? Can I, I guess appeal (not sure if this is the right word)? What can I do about this?

Is there any other legal advice y'all can offer that I haven't thought about asking for? Can I do anything about how controlling my parents are, legally speaking? Can they really deny me therapy and medical care?

I should also I add they sabotage any jobs I try to work because of the POA thing. I currently help my mother around the store they own and they pay me randomly and I'm not on any official payroll that I know of. Is this also legal????

I have so many questions and I feel so helpless and lost. I'm sorry.