I think that you have made a very good start to understanding this feeling. I'm so sorry that you've never been able to put yourself first, or have anyone else show you your worth.
I hear that you feel like you are taking something from someone, or intruding.
But maybe you're joining in at the table? No one likes to eat alone
It's hard to value ourselves as able to stand alongside others, I know. But I think that's a great way to look at it. Not as competing for anything, but standing alongside each other.
I hope that you can explore this feeling further cos it sounds like you are well on the way to something huge, and healing.
Good luck
Xxxx