I am not trained enough to tell you what could be wrong with you. I can however say this: My diagnosis is schizophrenia, and I had some very similar issues that you had.
I have been struggling with slight paranoid delusions since I was little.
I've always been paranoid. I don't remember much of my life at this point, but that's one thing I'm sure about.
I also talked to myself a lot. Like not even the normal talking, like full on conversations with myself.
I do that too. I don't have friends really, so I tell myself everything. I make up characters in my head and talk to them. Well, I shouldn't say they're made up. They're real people that I know, I'm just having conversations with them that I've never had before. I've noticed I get so into it that I will cry if they insult me. I'll laugh at loud if they say something funny. I'll love them if they say something sweet. I talk to them out loud, even though they don't answer out loud. So I appear to be talking to myself. I'm really not, I'm talking to them. I can't even stop it anymore, and I don't always realize I'm doing it. And, like yourself, I can go for hours in these conversations. Sometimes I get confused and think I've talked to someone about something already just because I imagine it and it seems so real. Although I don't believe talking to yourself is a sign of mental illness necessarily, I do believe it could be if you have a whole world of delusions and hallucinations that no one else can see you're talking to.
I have tried talking to people about it before but the only reaction I got was, you're lonely, it will pass.
I don't know if being so lonely can make you psychotic without having a psychotic background to begin with. Calling it loneliness and saying it will pass is hard to deal with. My mom always said to just get over it. More specifically, "Get over your bad self." It kills me so much that I don't even want to talk to her about the problems anymore. I'm kind of forced to though since I don't have anyone else to go to. But it's very condescending, at least to me it was. I hope you'll find a place to get cheaper help or something. I'm not going to lie, this kind of thing is very hard to deal with alone. And, as part of the disease we seek to be alone so that doesn't help anything. But medicine could make your life a lot more bearable if you can somehow see someone to get yourself checked out. I know that supplemental security income is helpful to people who have a diagnosis and can get it.
If you ever need to talk, feel free to send me a message or something. I know how hard it can be trying to get all the answers...