Wow, that's a lot to deal with. I can really sense the longing in your words. It sounds like what you really want is acceptance. Is that right?
You know, part of what you describe is really common in the military. Depression in the military is so widespread and it's often unacknowledged. It's hard for people to transition back into civilian life. And that disconnect you're describing when you say that you're surrounded by people but feel completely alone sounds a lot like what I've heard from other people returning from service.
It also sounds like there's some incongruence between who you are when you're with your friends, and who you are inside. Part of that is necessary because of the nature of our lifestyle, but that incongruence can definitely lead to feeling alone, isolated and depressed. Feeling like you have to hide part of who you are is always uncomfortable.
I wish I had answers for you, but all I really offer what I've learned from my own experience.
You say you won't be happy until you find a person who understands you, but I just want to caution you against thinking that a relationship is what will make things better. From my experience, you really have to take care of yourself first and then start a relationship, otherwise you will just end up contaminating the relationship with your pain.
The good news is that there are people who understand you. This forum is full of them. You can find acceptance here.