You knew that he was involved with someone else and that he was using you but instead of having the good sense to stay away from him you chose to sext and carry on.
You need to figure out why you did that because it is self-destructive and indicates that you don't have the personal maturity to make good choices for yourself. Focus on that and figure it out. Leave this man and his current girlfriend alone.
No.
You need to get your shit together.
You knew that he was involved with someone else and that he was using you but instead of having the good sense to stay away from him you chose to sext and carry on.
You need to figure out why you did that because it is self-destructive and indicates that you don't have the personal maturity to make good choices for yourself. Focus on that and figure it out. Leave this man and his current girlfriend alone.