Schizoid Personality that destroys my existence

Hello! Apologies in advance for chaotic message
I am 25 y/o, never been in a relationship, I am an extreme introvert, don’t like to socialise for a long period of time unless it’s my sister (I live with her and we do almost everything together) I have become aware of my personality disorder, however what’s weird to me is that 5 years ago I wasn’t like this. I have long history of eating disorder. I have social anxiety that doesn’t allow me to live my life/work/do things that other enjoy. I tend to have/used to have suicidal thoughts and I know that I am not made for live normal life eg being in a relationship/ have family/ even things like going on holiday/ doing something nice for myself doesn’t excite me. I have no need for an excitement. I don’t see purpose in living. I survive day after day but it’s draining. I have episodes of mental breakdowns. I have mood swings. My disorder holds me back from getting a proper job, the best option for me is to work from home and do not have a need to be with others.
I am aware that 5 years ago I wasn’t like that. Maybe not to this point.
There are some behaviours of mine that I can not comprehend. I am extremely possessive of my sister and quite controlling. Whenever she goes out I am not able to function properly, especially when she goes on a date. I try to do everything to destroy her potential relationships as I don’t want to be left alone.
I need help, can’t live like this, sooner or later my sister will leave and I need to somehow get a grip otherwise my disorder will destroy me.

My quick&dirty recommendations:
Become aware what it means to undergo an early childhood trauma and have a complex PTSD.
Become aware of the "principle of good reason" and that your "disorder" is already a compensation of that trauma.
Realize that there is no cure for this and that you and your social environment just can learn to get along with it better.
Between 20 and 30 moral values are developed in the brain: make fairness and honesty your moral values, so when you are fair and honest to others you can expect the same from them.
Reduce stress! Find out the things that are no good to you and avoid them.
Last not least: don't make you dependent on the help of other. Being self-efficient reduces stress. It's only you who can draw you out of the abyss.