Overthinker

I’m an overthinker always was and always will be but now that I’m dating someone that’s five years older then me I say things that I know won’t happen but still do think it will and he said that I shouldn’t be scared that we’re gonna break up cause we aren’t but I can’t help but still think it or be scared that I might lose him how do I stop thinking about this or prevent myself from being an overthinker before I lose my boyfriend the one good thing in my life. I think what made me an overthinker is being abandoned by my birth mom as a newborn baby and founding out that she didn’t want me and that just made me become an overthinker the fear of not being wanted.