Trying To Conceive, Taking Vitamin D. Belly Button Stretched, Cramping, Nausea, Having Unusual Period. Pregnant?

Hi me and my fiancé have been trying to conceive for 2 and a half months about a month ago I started taking 50,000ius of vitamin d because my gyno prescribed them to me since my levels are low, (it's genetic) I have been taking them now for 6 weeks I take one every week I'm just wondering why I'm not pregnant yet, I do know that since my fiancé has gotten home from the military my stomach has changed mainly through the past few weeks my belly button has stretched a bit it's more shallow now and I have cramping and nausea and I'm always really tired my periods are 7 days the first two of my last one were light then he third day was heavy then the 4-7 day was incredibly light which is unusual for me. I took a clearblue test a week ago to see if I'm pregnant it said not pregnant, but I have this bump and when I eat or drink it gets bigger it's right around my belly button also my fundus sticks out and it looks like a comma shape from my belly button to my vagina, could I be pregnant