It's tough when you stop being in a relationship with someone who's been in your life so long. It's only when they're gone that you realise how many little parts of your day were taken up by them, there's no cure for how to get over him instantly, if such a thing existed, heartbreak wouldn't exist. Honestly it is something you will eventually get over/ be numb to over time, it could be weeks or months, different for each person. An important thing you need to think about here though is he wasn't happy in your relationship. He cheated on you. You may have felt the relationship was fulfilling and amazing and you could see your entire future before your eyes with him but he (most likely) didn't. It's your first boyfriend and you won't necessarily realise this now, but there plenty of (better) fish in the sea, you'll find them. This one guy isn't the be all and end all, there will be guys after him. They won't be exactly like him, but they'll be great in their own ways and hopefully loyal to you as well. If you feel the need to cry now, do it, if you wanna sit on your bed and stare into space, do it (up to a point). let yourself feel hurt it's okay, see your relationship as a learning curve and an experience which you can now use to mature from. You existed many many years perfectly fine before this guy came along, and you will exist many more without him as well. You don't need him, it was just nice having him around, that's it. And remember, he wasn't as satisfied in your relationship as you, otherwise he wouldn't have cheated. Would you really want to continue to be in a relationship with someone who's heart isn't in it anyway?