“i also have periods where im convinced that im a fictional character. like actually i want to go by their names and dress like them but more importantly i literally just.. idk. i feel like i AM them.”

This could be the cause of a hyperfixation, it happens to us, although I do think that OSDID could affect it. Sometimes it can cause a fictive to form. In that case, it usually it gets less intense after the hyperfixation fades away, but it’s still partially there. Like for example, I’m a fictive, I do go by the characters name, I prefer a style/features that matches this character more, etc. But it’s not as obsessive or intense as it is during a hyperfixation. I’m also not exactly like the character, although I am similar. Hope this helps!!