Hi. You aren't making it up. This is how it is for you. Has it always been this way (apart) from this more recent 'not me' thing? Then you aren't making it up. Honestly you've described your experience really well. It doesn't sound made up and I imagine it doesn't feel made up either.
Everybody has parts of themselves. Every body has different sides of themselves that act and feel in different ways. Sometimes there is a smooth sense of 'I' ness between them and sometimes there is less. It sounds like there is some dissociation between your sense of 'I's. Not full separation since you still have a sense of yourself in each state, but the feeling/knowing/experiencing is separate.
I have been diagnosed DID and the separation of my parts goes a step further than what you describe here. Those other parts are definitely not me. They are them! Each part has a very distinct sense of self that does not include the others in experience/feeling/sense of I etc. That is changing through therapy and we have a lot more co-consciousness than we did before, with some parts at a least.
But it certainly doesn't sound like you made any of this up for attention. It sounds very real and very problematic.