Worried?

This may seem silly to some (or most) but I need a little reassurance if anyone is willing. My boyfriend is going into the Marines & has barely even left for boot camp yet. I’ve been getting by for the last few days but expect things to fluctuate for sure.

My main concern is something he’s scared about too. He’s afraid I’ll go off while he’s gone & find someone better & move on & etc. Which I can’t even fathom doing. I’ve been with him for 2 year prior to enlistment, if I didn’t have intentions of staying I would’ve left by now but he’s my absolute world. However in my mind, I feel like he’s more likely to come home after being “changed” at basic & decide that I’m not what he wants anymore. That maybe I won’t be up to the standards he is going to be taught. I mentioned it to him & he tried to ease my mind about it saying that he wouldn’t & that I mean the world to him & that he wants me here when he graduates and comes home. It just is sitting in the back of my mind & I know it’s probably like all the other doubts I get but this time it makes me feel kinda sick to think about because I love & care about him so much.

So I guess what I’m getting at is, has anyone else had this doubt & how did you get through it? Or is there anything you can suggest on how to push it out of my mind/get through it?

I know a lot of you have been at this a while & I’m just barely getting started. You’re far stronger than I currently am & I thank you for what you have/are sacrificing as well as any help you can give me.

*I wanna add that we are younger - fresh out of high school/18*