I want to leave my husband

I've been feeling for a while that I don't love the man i married like i did in high school. we got married young bc he's in the military. everything seemed great. then we moved in together & he started at his duty station & he just turned into someone else. it was the worst 5 months of my life. so i went home for about a month & the entire time he was texting me how miserable he was home alone taking care of the dog by himself & coming home to an empty place. i felt bad for making him feel this way so i went back. he had scheduled counseling for us & i thought life was going to be great. well i got pregnant. so now i'm 18 weeks pregnant at 21 years old & i'm so miserable. we just don't click like we used to. & i don't have the courage to leave. idk what to do.