The Other Woman didn't know (long vent)

Been dealing with this guy for a little over a year and a half now. I thought he was great til I found out he's been with his baby mom for the past 4 years. When we first met at my new job, we clicked and he randomly asked me for relationship advice from a female perspective. He was ready to leave her but they worked things out. We slowly became casual friends. He sometimes flirted and goofed around, but I never took him seriously. I did tell him he needed to stop tho, because I don't mess with guys that are occupied. Plus I was dating someone at the time. I told him that if he wanted me, he needed to talk to me when he's done with her. Time passed and he asked to take me out on a date.. I told him that I couldn't go because he has a gf. He later told me this story of how they broke up. After time and persistence, I was free so I finally let him take me to dinner. I told him I was skeptical about talking to ANYBODY with a babymom because I didn't want the baby mama drama. He told me they weren't together, they have a mutual respect for each other because of the kids, but they've both moved on & she wasn't the type of woman to cause drama. We continued to grow close and into more. Much more. We discussed our future together, careers, going into business together, baby names, marriage, regular things ppl do in relationships when they take one another seriously. He was great. Until I found out a few weeks ago, him and baby mom were still together and NEVER broke up. She called me and began getting indignant, asking me who I was and why I kept calling and texting the man. We exchanged a few choice words and I hung up when she called me a home wrecking side whore. She was irrelevant to me nor was she worth my aggravation... I confronted him about the call and he told the truth in saying he was still with her and has been for the past 4 years. I couldn't believe my ears. I was hoping he'd say she was just a stalker ex girlfriend. I was devastated and told him to just leave. When I see him at work, He keeps trying to plead with me but I want nothing to do with him. All of this apologizing and trying to proclaim his love for me, but he's still with her. Trying to say it's only for kids. He's a liar, a cheater, a manipulator and I feel like such an idiot. There were two events that happened as far as she was concerned and he made me feel like I was insecure and delusional for feeling like something was up. I haven't spoke to him in 3 weeks. He has called everyday leaving long voicemails on my phone. I can't believe nobody in his family or none of his friends would say to me that he's still with his girlfriend when I came around and we've  talked, laughed, and formed relationships. His sister doesn't even like his children's mother. It gets worst. Today I take a test.... Positive. I'm livid. I'm supposed to be happy but I'm embarrassed, pissed off, devastated and wanna rip this child out of me. My first child will be to such a prick. I keep thinking of how I'm going to go through all of this pain bearing a child for a man that was deceiving me the whole time. I haven't even told him and a major part doesn't want to. I just want to take care of this child without ever telling him about it. Of course I will eventually, but I'm just really trying to process all of this. What am I going to do? I'm terrified, angry, confused, heartbroken. I feel like everything keeps getting worst for me. And I just want to make this all go away.