thats a very very obvious thing right there. She seems like shes trying to hide all possible ways for you to find out its not yours. Im not sure about her, but If I knew you were the father of my baby, I would not be dumping you. I would request a DNA test, but the thing is, im not sure if YOU have to pay for it. I would look into it. But according to what I know, seems like she wouldve been ovulating before you two had sex. Which would lead to only one thing!! cheating. but DNA test really is the only way to prove... orrr, call the doctor she goes to, and ask him which day he estimated to be her conception date. If it was the 18th, then you are ok, but if it was before, Im not so sure who the father is. Good Luck buddy.