Is my relationship fixable?

We have been together 4 years, but the last two have been horrible. When we met I was 6 months pregnant and he had a little girl. Everything was wonderful until we found out that his little girl wasnt biologically his. He became distant and eventually even cheated. I cheated and even had a baby outside of our relationship. We had broke up earlier this year, but got back together in July. I just found out that he has been cheating on me since September and even had a ring on this girls finger. Worst of all he had manipulated me into believing that we could have a polyamorous relationship (I am bi) and had the girl living in our home for a few days. I recently heard someone say that love is as love does and love doesnt hurt. So if we love each other so much why do we keep hurting each other. Is it possible for us to find our way back to each other. We had such a profound love for each other at one time and lost sight of that due to poor communication. I miss us. Is all this fixable?