Feeling stupid around my friends

My friends are so smart and educated and I can't understand why they want to be friends with me when I'm so stupid.

They always get into these deep, thoughtful discussions about complex topics and I feel like I can never join in on them because I never have anything smart to say. I hardly express my thoughts out loud because I want to sit with them and reflect before I say them but even when I do express them, I feel like they come out wrong and I always get proven wrong or my friends give a counterargument that's smarter than what I said. I know it's not a competition but I feel so incredibly stupid when my own thoughts aren't ever smart enough on their own.

I've always wanted to be smart and thoughtful but I don't think I'll ever be that. It takes forever for me to actually pick up on things and difficult topics. When I read/study I feel like I have to reread things a hundred times before I get it and can remember it and use the knowledge. And whenever my friends bring up the things they have read (from the same pages I have read) I feel like I can't catch up with what they're saying. It's like I'm always ten feet behind their knowledge and intelligence.

I absolutely hate that about myself. I feel like I'm so stupid that I won't ever be able to contribute or amount to anything in this world. I still can't believe my friends even care to bother with my or how my boyfriend can stand to be with someone so stupid who can't make up her own smart thoughts.