How are you not scared that your SO could leave you?

I've talked to 7 ish guys last year I live in the middle of no where. these were guys long distance. I'm talking to a new guy for 3 months and i really really like him but i know now that he could leave me like all the other 7 guys. I'm trying to not think about that and still love him fully. It's better to love all than to give it half heartedly in fear of being hurt. But like sometimes i think about him leaving at least couple times a day and break down crying or if he didn't reply for some time I'm like oh he might be fucking someone else. : ( I just have PTSD I don't know how to stop it

How are you not scared that your SO could leave you?
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