Should i demand my husband and his ex-wife take a paternity test on her new baby?

Ok here's the background. I have lived with my husband for 4yrs. We have five children (2 mine three his none together) I have felt for the whole time that the ex-wife called the shots. My husband jumps and runs for her consantly.I have accepted this we have gone to counciling and have had numerous arguments. He agreed he would feel the same if in my shoes.Just like every unhealthy relationship it gets better for a while then back to the same ol' same ol' I accept this and slightly understand it. Me and my husband offically tied the knot in July. of this yr. In November we found out she was pregnant. The ex-wife had just gotten back with her husband and two-weeks later she finds out she was pregnant. Well the ex-wife's husband left her due to the fact she was pregnant and obioulsy not by him. In May the ex-wife tried to change her last name back to my soon-to-be last name. I told my husband I would not marry him if her last name was going to be his. He spoke to her and resolved the issue. In June my husband came to me asking to get $400 a month for work. I was confused and explained to him if we had an extra $400 then we wouldn't be behind on student loans, and JOKINGLY replied" for what child support". He was defensive and started yelling at me that it was his money. I said if you need then get it.
The ex-wife gave birth in August to a little girl. The day she brought the baby home she went by my husband's mom and dad's home and also our home. As soon as she pulled up my husband left. Odd right?
Last week she brought the baby over again, and I have to say the kid looks just like the rest of my husband's children and also like my husband. I told the ex-wife what I thought and she left smarting off " well even $20 a month will buy a pack of diapers and I don't have to share her with anyone, again i questioned my husband and again he denied it.
Last weekend I went over to my mother-in-law's home to help her decorate for halloween, and she had pictures up of the new baby and just gushed and gushed over the new baby. I just bit my tongue and went on about decorating.
What do I do how do i handle this situation? It is a catch 22 if I demand it and it is his we are finnished but I will be able to sleep at night if the baby isn't his then I just look crazy and foolish but will be able to move on....