Boyfriend doubting us, I’m his first

I need some genuine advice. I’ve been dating my boyfriend for 6 months so far and we have been having an incredible time together. We are so happy and having fun and have bee n goal setting and planning a lot together. The issue is I am his first everything. He didn’t have luck growing up with other women and was so happy to have me and have met me but now it seems when his mood is low he doubts us and he says things like he wonders what else is out there. He is a brutally honest person who can’t lie and says what he thinks before thinking and regretted saying that completely but it shook me because we are really falling for each other and then he pulls back. I don’t want to start feeling insecure or stressed over this. He makes me feel loved and amazing most times but then says things like this that makes me feel like we’re not enough for him. I understand where it comes from but also am now being concerned and cautious. I’m scared it’s like a ticking time bomb and a doubt that he won’t be able to get ivermectin not knowing what it’s like with someone else. Please help, what should I do here? He apologised so much but I’m scared of it happening again or pushing us apart or one day it just ending and me getting to involved. I’m all in but now feeling defensive or protective over myself which I need to relax a bit too but any advice please help.