i just want everything to be okay

I've been dating my boyfriend for almost 4 years. We are high school sweethearts and both now 20. He joined the military and was in Korea for a year. During this time in Korea, things changed. He was drinking, partying, got into fights, and even found himself friends with a fellow solider who was stealing and selling prescription pills. He also would promise to skype me and then either forget or say he was hanging out with his friends.

One night, we said we would skype at 12am my time (1pm his) and to my absolute horror, he didn't answer me for 9 hours. When he finally did, he said he was jumped after smoking a cigarette outside by himself. I was hesitant but believed him. He never gave me a reason not to trust him.

I started feeling not so sure about our relationship when he got extended by 3 months to stay in Korea. I was nervous about him drinking, constantly worried about him staying out of trouble. I was just worried and stressed for those 3 months and then last week when he came home... it just... poofed. My boyfriend was back and we could finally be together again.

Something didn't feel right though the week he was staying with me at my dads house. I loved being around him but things would suddenly get awkward and I eventually burst into tears during an outing. I told him how much he hurt me and he said how sorry he was and how he would like to do better. I calmed down and thought everything would be okay.

Sunday, just yesterday, is when I realized I don't think I know my boyfriend as well as I thought I did. He was sitting outside with my stepmother and one of her friends. A very inappropriate topic was brought up and he apparently was very animated while talking about it. Very NSFW and he talked down about a group of people that did a certain NSFW profession like they were lower then dirt.

I had never heard this. The boy that i fell in love with would have never talked about people this way. I was horrified. Even more so when he said that he tagged along to one of said bars. Drinking I was concerned about but never cheating. never cheating.

so i asked him to leave and report to his base early. i remember saying something like "ive been wanting to be with you for a year and now all i want is to be away from you" and the look on his face killed me. he was sobbing when i hugged him before he got in the car. i couldnt see him leave.

before he left he said all he wanted was for me to trust him again. he wanted to gain that back no matter how long it took. Now i find myself sobbing on my bed typing this because i honestly cant tell if hes lying or telling the truth. ive asked him so many times just to admit something, anything, so i could see he was trying and we could maybe work on us.

cheating is just something i cant wrap my head around him doing. he cares about me so much i know he does and part of me wants to believe everything hes saying but another just isnt letting me. he swears hes never lied to me while he was there so why do i have these feelings? hes never told me things and i find out and that can be an issue too but the things he is telling me right now i just want to believe so badly.

So now I'm stuck. Do I say "okay. lets work on us." and go along with the relationship and continue working as hard as i have been? I love this man so much and i want to experience so many different things with him. he was my first in absolutely everything and i really want him to be my last.

Do I say "okay. lets take a break. nothing on the side. we're still committed, just take some time and see where we find ourselves." Hes two hours from my house at the base and that distance is fine compared to the 13 hours we had.

or the absolutely dreaded. " ---, i really dont think this is going to work right now. where we are in our lives and who we are as people... yadda yadda yadda"

how do i know if hes telling the truth or lying to me? how do i figure out what to do next? I hate the feeling of him actually telling the truth and im accusing him of lying still. please i need some advice from people who arent in my family and friend circle. i really just want us to be happy and okay