Okay, i seem to find my way to threads like this so allow me to break this down and cover all the bases i can.
First off, to answer the initial question “can i be a demon?” Well, the origins of the word demon comes from the greek word daemon, which roughly translates to spirit (or as Socrates put it “divine principle or genius”). Seeing as you are essentially a spirit wearing a suit of flesh to exist in this world, you certainly can be considered a demon. The whole brimstone, horns and pitchfork aspects were just a politically convenient way of encouraging others not to worship beings not approved by the ruling power at the time. In that sense of the word, no you are not a demon. Just a troubled soul who has walked through hell to get here.
Now, no one on this forum can provide psychological help. That is not our job and resources have been provided for such as above. We can suggest rituals that may help but the actual treatment you will have to find else where. As always, I recommend the better help app if you are struggling financially to get said help.
That being said, I have written something in the past that helped me when I was in a dark time where my life could have very easily ended. It is a bit extreme but sometimes extreme measures cause big effects. DO NOT USE IT AS A SUBSTITUTE FOR PROFESSIONAL HELP. I will not be responsible for it. Instead, use it as a supplement for your healing process. Hopefully it helps in some way