We can never really know who we really are i guess, like you said, we are constantly changing, i'm not the same person as i was 2 years ago, well in big lines i am, but when look back at who i was and who i am now, i've changed a lot, especially with who i was as a kid, teenager, etc.
The overanalyzing part is something i can relay to, i tend to overanalyze EVERYTHING, all the time, it's extremely energy consuming.
I think it's because of my heavy cannabis use, i started to smoke weed when i was 13 and stopped almost completely when i was 27, i always thought of it as a healing plant, but a lot of my personal problems have to do with my inability to use cannabis appropriately.
I'm not saying this is the case with you, but if you are a heavy cannabis user you might consider taking a break from it, or stopping entirely.