Make a decision. This is a life lesson. If you broke up for a reason, is that reason still valid? If it is, then your decision stands. What is going on is that you are feeling bad and you are trying to relieve that feeling. This is a very common thing that people do. They get back together because they feel so bad. This is a bad reason. This person will say bad things about you IRRELEVANT of whether you are together or not. There are plenty of fish in the sea. Time to go fishing.