An update to my last post... I tested again this morning and still BFN!

I waited a week from last Wed. to retest! I feel like I'm losing my mind, I think there must be something wrong with me! Even though I'm testing BFN, I still have symptoms of being pregnant (gassy, nauseous, can't stand to smell certain things, prssure in abdomen, now getting cramps in my legs, going to bathroom alot, and really tired)! My husband thinks that my breasts look and feel fuller, I don't think they do! I was told that the symptoms might be brought on by the prenatal vitamins the dr. has me on?! Then yesterday (1/25) I had some CM - if I'm not pregnant AF should start on or around 2/14!

But what else could be wrong with me?!

How far along would I be if I am pregnant? (BD on 12/31; implantation bleeding or spotting on 1/14-1/16 - with all the above symptoms. Please help, I'm so confused?! Sorry for the long post! Thanks!