Do you think this is NORMAL behavior?

I cheated on my boyfriend of 6 years. I loved him a lot but was sick everything. We were living with his parents, and he has a crappy job. I had an ok job and even though we had hardly any bills, I was paying all of the existing bills and debt and we were still ALWAYS broke. I got fed up with it and was contemplating leaving him. He still parties and acts like he is 17 even though he is just about to be 30. when I told him what happened, he went nuts and told me that he can't live without me. Since it happened with someone I work with, he called my work and told them what happened -- told them that I cheated on him and even named the guy's name (we'll call him Ted), and told them that I would not be working for them any longer. So we went out of town to "rekindle" our romance (I footed the bill). I thought everything was going good. I felt and still do feel horrible for cheating. Well, a month later, we broke up. 3 days after that, I found out I'm pregnant. I never questioned paternity - I know it's my ex's. My doctor ured me that there's no possible way that it could be Ted's. Now it has been 5 months and we are back together, but he is threatening to do all kinds of stuff to the guy I cheated on him with. Like threatening to set his car on fire, have him beat up. I seriously can't take the stress. Especially right now. And when I told him that I am going to tell Ted, he says that I'm not loyal to him and that this is the only way he can get past what I did. Is this normal behavior? I'm very scared that he will go through with it. And if I knew about it and could have stopped it, or at least given a warning to Ted, I don't feel that I can deal with that. I want us to be a happy family and get past what I did, but I also want him to grow up and not be so damn childish and irresponsible.