Why is it that when your boyfriend cheats on you, you are the one that does all the suffering and he and the other person go on like life is just grand and they are untouchable?

Its because you are the one betrayed, and cheated on, and in times of great hurt, and pain, we seldom see the suffering in others. Not that they are suffering mind you, as being caught cheating is nothing compared to being betrayed, so it's a matter of perspective. The cheaters just are not in as much pain as the cheated on, generally. Oh they have guilt sometimes, but they don't have the same shock of discovery the cheated on have to go through.

Cheaters have control of their actions, the cheated on cannot control the cheaters. Then there are the lies that hurt us but helped them cheat! Ever see a cheater that didn't have to lie?

It is because for him to cheat, it means that he never appreciated you, the feelings of depreciation, rejection, and betrayal all at once is what makes you feel horrible, on the other hand, he didn't have any of those. All you do is let time go by, can't get easier than that.