Return the ring, get yourself a health check, then smash any of her possessions that you can, and burn the rest.

That's 5 years down the drain. Stay strong op, That bitch never deserved you anyway. (Assuming it was a clear case of cheating.)

Be very glad you found out before you gave her the ring. Get pictures of everything, then when ready wait until she is out and have all her stuff put on the front lawn, attached the picture, and change the locks.

Are you positive it was Somone she was cheating on you with? There have been planets of times where my friends and I will all go out and have a few drinks and get Somone to be the designated driver to drop us off. The man could of been a friend or even a Uber driver unless you saw her kissing and groping him or she said she was cheating on you I would not assume she was cheating on you. Give her a benefit of a doubt and talk to her first before you scream cheater because that’s a little messed up.

Sell the ring to the “other man” for a fat profit, and use the sweet cash to by hookers and beer.

Propose to her (probably not in a public place as this can make you look like a jerk) and if she accepts, tell her about what you saw and don't give her the ring. Remember, karma's only a bitch if you are

At least you caught her BEFORE you gave her the ring.

That’s what you get for waiting 5 years to propose.

Outside of her being dropped off by somebody what proof do you have that she cheated . She could’ve gone out with friends and I have been the last want to be dropped off. If based on that you were convinced that she cheated maybe a F her life.

Better return that ring! It's a good thing you found out before you popped the question. Still, that sucks, OP.