lost and alone!!

Today is my living son's 6th birthday. He was very much excited since long for his birthday as when i conceived with my angel i told him that he was going to get a sister close to his birthday. Its hard for me today to manage my son without his sister and surprisingly he was angry on god.. i never knew he would do that he was telling that"god took away our sister..and so on"i didnt know what to do.but i want to be strong for my son.I truely miss my daughter very much.We had lot of plans planned together but she left us and went far far away.I was angry at god first but now i am out of it. I dont know how to control myself as my brain and heart is constantly thinking of my baby.I am living like a toy doing the things i am supposed to do without any heart ,and without any life and emotions in the things i do. I feel like i am numb and with a shield of darkness around me. I want to try again after few months but at this point my heart is not in a position to decide on anything or plan anything as i scare that my plans will never work out . I am scared that "what if i dont get pregnant" am i still fertile""can i still get pregnant" "will i be able to have healthy baby"....and so on.my heart is crammed up with all these questions and fears.