How to trust again after been cheated on in the past.
Every relationship put dents in our hearts and we tend to hold on to them in future relationships. The first step is forgiveness. Forgive the mate that cheated in the past. Not face to face but mentally. Let that hurt go.
Give your new mate the benefit of doubt. Don't accuse them of stuff even if the situation is similar to a past situation. Trust them until you have a reason not too. A in your face reason.
Thank your past mate who hurt you in the past for the experience and teaching you and take that lesson as a stepping stone to finding the mate of your dreams.