I can't decide

I need to know when to stop and be firm with my decision. I'm afraid of losing someone who has been my priority for eight months. I found out he slept with his ex-wife and continued to lie to me. Forgive him already, but I can't forget what he did. When he said sorry, it was so easy for me to accept him, but when I was reminded of all of the mistakes and lies he made, I instantly made the decision to leave him. Then, when he is about to leave me, I am again trying to stop him. I'm not sure if I am afraid of losing him, of being alone, or maybe because I love him so much.

We live together in the same apartment and do what normal couples do. I'm not sure how I can fix my life knowing that the situation will be circling around: be happy in love, be reminded of the lies and mistakes, split, be back again, fight, and split.

I have made a decision before to start a family with him, although he already has two children with his old partner, is married to another woman but has no child, and is not yet annulled. What should I do? I am a single career woman who's longing for someone who will love me and take me seriously. I never asked for money or material things and have been a supportive partner—emotionally and physically—serving him and financially helping him.