I'm his first, will I be his last?

My boyfriend and I have been together about three years, since we were Juniors in high school. My senior year I got pregnant and had our daughter, who is now almost two. We've been living together for almost two years now. When I met him, he was a virgin and never been kissed. I was not a virgin, but I had only been with one guy and it wasn't even a relationship. We're each other's first serious relationship, and we've been through a lot together - from my hectic preeclampsia pregnancy to his Mom leaving the family, and my Dad losing his house, to his Dad abusing him - and graduating together and becoming adults side by side - we are each other's everything. We do everything together. Last August I caught him on a secret phone watching porn (I'm strongly against it), and we worked through it. We've gotten into a lot of ugly arguments, but we always work it out. He's thinking of joining the army and we'd get married before he ships off to Basic training. He'd be gone for more than six months, only seeing me once, however after 10 weeks we can text. I've been told all kinds of horror stories about guys cheating and going to strip clubs behind their wives and girlfriends backs during training. Does it sound like he'd do something like that??? Advice please!! 😥