I'm dating someone who has been cheated on. What should I do?

You can't change what happened to this person, the only think you can do, is do this person right, don't hurt them.

Support them. Reassure them that you love them and only them. Don't get defensive if they say they think you're cheating. Cheating is a tricky subject to deal with, show them compassion.

Your partner has likely experienced feelings of betrayal through their trust being broken. Be gentle with them. I would recommend restraining from inquiry about their past situation without them being the first ones to speak about it. However, it is always considered a positive move to let your partner know you are there for them, should they wish to discuss this topic with you.

Make sure they're comfortable and if they want you to, reassure them you're not cheating on them. If needed, let them monitor who you talk to and what you tell them if you're comfortable with it :)

First of all, if your partner has been cheated on, then he/she might find it hard to trust someone. If he/she chose to be with you after he/she has been cheated on then consider yourself lucky. Please don't hurt your partner and always be transparent to each other. Good Luck!

Be as supportive as you can be. Is understanding that after such an experience he has some trust issues but is important for your partner to know that you are not their ex and you will do different things to show so. Don't forget that also the relationship shouldn't be about you proving yourself to them but if it becomes a constant battle then you two should talk and part your ways if you are unable to work through this.

You should let them know that you won't hurt them and you must keep their trust as well as you can..

maybe start off by telling them what they have been through nobody should ever have to feel that pain and make it clear you wont do it so they know to trust you

Take things slow. Let them see and know that you will not cheat on them. Show them that you are trustworthy and you are not there to hurt them.

They might have some trust issues understandably. Just make sure you can convince them that you love them & you promise you wouldn't do anything like that. Its all about gaining their trust