You aren’t in love with him. I suspect you have amazing sexual chemistry with him, and because those feelings can be insanely intense, you mistook it for love. I would also bet that a large majority of human beings who have ever existed have done the same thing — I’ve done it myself more than once.
You two haven’t been dating long enough for real, solid love to grow. And you never will, because he has made it 100% clear that he will never put in that effort or prioritize you.
But like others have said, as long as you let him tease you with little tastes of what you can’t really have, you will not get over him. So cut off all contact immediately. You can let him know you are doing this, but don’t let that turn into a conversation. Just tell him you will no longer be contacting him or responding to his contact, and then STOP. Block him on social media. Do not answer his calls or respond to texts or IMs. Not even once. Not even if he makes up some story to try to engage you. Do not engage. It is the ONLY way you will move on.
You can allow yourself to feel sad and hurt, and to miss him, but try to avoid wallowing. If you find yourself wanting to peek at his social media or ruminating about whether he might ever leave his wife, force yourself to do something else. Call a friend. Lose yourself in a great book or show. Work out. Whatever focuses your mind on something else. And overall, just start doing lots of things that are good for you and and make your life better. Whether it’s socializing with friends or starting some new healthy habits or taking up a new hobby or advancing your career — do something for yourself.
Over time you’ll realize that those obsessive thoughts are fewer and farther between. And one day you’ll think about him and realize there’s no emotion there. And you’ll know you’re free.
I know this works because I have done it myself. It wasn’t a few months relationship, it was 15 years. And even at the end I was wildly, passionately in love with him. And still, he left. And then continued to string me along for about another year. Only after I said a very permanent “goodbye” was I able to start healing. And that freed me to give myself fully to the man I married this year, who is so much better for me in uncountable ways.