Should I contact my ex about why we broke up?

I recently broke up with my ex girlfriend about 2 1/2 months ago. We were together for about a year and a half and also lived together. I do believe it was a bad breakup as it didn't end easily. I'm still having trouble with it, but I don't know what exactly is bothering me. I can't really pinpoint it. Part of me wants her back, but I know thats not going to happen. I am trying to move on without her, but I still have dreams about her on occasion. I haven't communicated with her in about a month or so. I'm unsure if I should maybe contact her and speak with her about why everything ended the way it did - because I don't really understand any of it. I kind of want to get some understanding and maybe that might help me move on quicker, but at the same time I don't want it to set me back. I just want to get some unbiased opinions on this. I can provide more details if needed. Thanks.