imho - cheating is any action toward the person of another sex that could indicate an interest in them, anything he wouldn't want you doing or would not willingly do in front of you without pause.
I've learned, in relationships we choose what we want to deal with. What you deal with is up to you and often based on your own value system. How much you love yourself will determine how much drama you put up with. It looks like you LOVE you which is why he is now your "ex" bf. I'm sure it's hard, but a better man will come along and you will look back on your ex and be thankful you didn't stay. The pain takes time - 4 years is a long time to invest in a relationship, but better it end now than 4 years from now as it could only get worse. If he was truly regretful about his actions, that would be different. You both could work it out and keep it moving- but it doesn't sound like he's sorry- it sounds like he is arrogant and selfish. Even if he didn't think he was wrong, if you feel like he wronged you, he should do what it takes to make things right.
Oh & one more thing- sometimes you have to listen to family with one ear and let it go out of the other. Loving yourself requires that on occassion, nobody agrees with you but you & that's because nobody is gonna love you like two people: 1) God & 2) You.
Sorry to ramble-I hope things work out for your best interest.