HELP ME PLEASE!!!!

I'm 19 and I'm 7 weeks pregnant, the father of my baby is 32, married with children. I know he has a right to know I'm having his child, but I can't bring myself to tell him because I fear for the worst (ruining his marriage etc) also my family don't know he exists so I have no idea what to tell them when I tell them I pregnant. They will want to know who the father is!!! Wahhh I'm so lost right now. What do you guys think I should do??