I am so sorry you are going through this Kiwi

You deserve to be loved wholly and completely for the beautiful person you are inside and out, without reservation. For a LONG, LONG time...it just hurts like the worst kind of he11 and it feels like it'll never get better. Hang in there, dear, it does! And you will see this person was never really as great as you once thought, and may even wonder why you put up with him.
From experience, do not u
nder any circumstances take him back. A person who leaves you, is a person who leaves, as they say. All taking him back would accomplish is showing him you are willing to accept his lousy behavior. He may very well try..if his new thing doesn't work out...don't be surprised if he does come crawling back. My ex did this multiple times. I didn't love myself enough to break the cycle until very recently and it is the BEST feeling to walk away and not look back.
You are far better without someone who told you he wouldn't marry you for such a reason! And an excuse though it was, what an incredibly low and hurtful thing to tell someone you allegedly love! There are people out there who will love you no matter what, forget that clown. And he's sucking up your energy like an emotional vampire, why is he still texting you? He should back off and let you be.
Take it day by day, try to eat what you can. And lots of self love and care: be lazy as you want, watch movies all weekend, cry your eyes out, take long bubble baths, listen to music (my Adele playlist was on constant rotation for a year I bet). Be indulgent, keep busy. It's going take time mostly, but you will get there. (((Hugs)))