One point you made was being afraid of "being crazy". No one who fears and worries about being crazy is ever crazy. Crazy people never care or give it a thought
As to being an angel, whatever you are is you the I am bit. Right now that is in human form. In the past angelic form. Your form is not you it just houses you, it's a body a vehicle
I have memories of being a thing far from human form. We all have our histories and they are wide ranging
Don't go check if you are or not. You might get some plonker that cant see the wood fom the trees.
If you feel so intensely just accept it and let the fear seep away Tell your angel bits how lovely they are and how you appreciate such a history
We are all unique and it is lovely to appreciate that.