Is it really my fault?

I broke up with my ex girlfriend Kate after two months together and I called her boring which I didnt mean to just because I really like another girl. My ex wont talk to me ever again and she was all happy I d never see her like that before. My men friends started to like her and want to date her. I felt betrayed so I didnt care then I date this fine woman Cindy and we been together for 11 months then found out that she cheated on me 4 times with another guy who been close to me. I broke up with her and found out my ex is still single so I hope I would have a chance to be with her again but Cindy said she ll kill herself if i wont get her back so I decided to take her back so she wont kill herself. I really want Kate back but I started to seeing her with another man Rob. I need to tell her that I love her but Rob wont let me. Is this really my fault???!!! Can I have a chance to talk to her? Do u think she will take me back? What should I do with Rob??