Relationship advice needed!?

So my boyfriend of over a year is starting to act really different. About a month ago, he drunk texted his ex saying he loved her, and she was amazing, and the conversation ended up going to "if I'm drunk enough I'll end up being dtf." and she goes "fine with me ;)!" We got into an argument, I almost dumped him but I just felt terrible. I didn't know what to do. Although I've heard the saying that drunken words are sober thoughts. she has cause a lot of problems in our relationship and he said he would stop contacting her, and block her from everything, but I don't think that has happened. We're all good now, but I still don't know if I could trust him. He's been acting different ever since that happened. He will text me one day and tell me how much I mean to him; then the next 3 days he will go off and nto text me. If I text him first out of those three days, he'll reply but I feel like I'm too clingy if I do. I feel like he still talks to her, and I wouldn't doubt it because way long before we dated he told me he was completely in love with her, and nothing would change that. I'm pretty sure they still contact each other. I've confronted her before but she won't back off. What Should I Do About My Boyfriend?