Messy situation

So my ex and I had been together since May 2016. I broke up with him May 2018 but we've kind of stayed talking. I love him but I'm sure he's fooled around with his ex. He denies it when I bring it up but he followed her on social media and she was being invited over to his parent's house, she was stationed at the same base as him since March 2017. He didn't give me a heads up saying "Hey, this happened but I had no part in it" I just found out through social media since I'm friends with his mom and she'll post stuff on his mom's profile. She even sent me a friend request. We're long distance too and had been for the most part. He used to visit every month. Then he stopped visiting since January and made excuses about it. He said he's depressed and I'm trying to be supportive but he's given me every reason to walk away and for some reason I can't. I met someone else who was a great friend to me and we both learned back in May 2018 that we liked each other after I broke up with him. Now my ex is trying to win me back and promised to quit his job and get an apartment to be with me. I don't know what to do because I'm still in love with my ex but I don't trust him and I don't believe that he will follow through with this because he's been saying that he would get an apartment with me since December 2016. Should I try and remain friends with this new guy who has been there for me a lot lately? Or for my ex who is trying to get past his depression and win me back? He isn't terrible either but ever since he's been depressed at the start of this year, he's changed so much and I don't like it with his drinking and tattoos and unwillingness to Skype or communicate, yet, I still love him despite the fact that he shut me out.

Edit

The guy I've been talking to knows I'm in love with my ex and I've told him I didn't want him to be a rebound because I felt that way with my ex. I'm not in a relationship right now.