MY EX AND HIS NEW GIRLFRIEND....?

Ok now first and foremost, dnt judge me from what you hear on this situation. Anywho, my ex and I were dating on and off for 2 yrs and then he cheated on me. And the crazy part about it, he left me for the new girl. So I tested him to see how serious he was and asked him did he wana have . Lol and like a guy, he said yes. I wasnt intending on having anymore feelings towards him after the break up until he texted me saying how he miss the pictures I used to send, early morning texts, etc. And now I keep thinkin about him and I know that he's not goin to leave her. So how do I get over him? Like ASAP?