That's a tough one. If it helps any, you are not alone. Many, many loved ones and family members experience this because many, many civilians join the military every day. Why not? After all, the military is a big transition from civilian life. Also, unfortunately, civilians don't think of the good, just the bad and the ugly.
So, are you "wrong to feel this way?" I cannot answer that. I cannot tell you how to feel. However, I ask that you trust your boyfriend and his decision. My guess is that his decision wasn't on a whim. He thought long and hard on it. So why not trust him? While you're at it, trust his future team and supervisors. They'll look out for him and he'll look out for them.
A lot of folks seem to be taking this article the wrong way. In other words, I didn't write it to discourage or scare anyone. I didn't write it to bash the military. I meant to celebrate it. It's an amazing experience as long as you do your best and put your country first. Trust your boyfriend to do that.