Just be honest with him. Next time you get together tell him there's something you want to clear up first. Explain that you are getting divorced, have been separated for over 1.5 years, and you said you are single because that's how you see yourself. Sorry if there was any misunderstanding but you just wanted to make everything clear moving forward.
Then get the D papers filed and if H won't do it, do it yourself. If you're not ready to file then you're not ready to be in another relationship.
If you love somebody, set them free. http://tinyurl.com/2empx2g