Wow, that is a very hard situation to be in. I am so sorry this is happening to you. A lot of the time, in life, people turn out to be different than what we expected.
I, too, went through a really hard break up about 7 months ago. To make a long story short, I was engaged to a man. We had the whole wedding paid for and planned out, when unexpectedly one day he admitted to me that he had went to an Asian massage parlor and cheated with a prostitute (I later found out it happened way more times than I knew of, which did not surprise me at that point.) I took some time to myself and eventually decided to call off the wedding and dump him. After that, he ended up also admitting to me that he also is into men and is bisexual. I was lied to about who he was, and felt like I never knew him at all...because I didn't.
This past 7 months has been the hardest time of my life. As I am sure, the months following will be very difficult for you as well. The satisfying part is knowing that you will no longer have to worry about any STDs you can get from him being a cheater, you won't have to worry where he is or who he's with because it won't be you who he is playing anymore, and just knowing that someone/something better awaits for you in the long run.
You may not realize it now, but he has just made you much stronger than you yet realize. You will now be able to seek and find the love you will never get with him. You will, one day, be very happy that you have been freed of his selfishness and lack of a person that he is. You are right, he is a coward.
The most disheartening part about this, is the child involved. Your child. It is one thing to leave your partner, but to leave your child is the most cruel, heartless act of all time. I hope, for your child's sake, he ends up coming around to his senses.
I know it is hard, but you will get through this. I wish you the very best. Stay strong.