I'm going through the same thing. For three whole weeks before my "period" I was having mentral-like cramps that were lighter than they would be for a normal period but still unmistakably period-like and very sensitive breasts, to the point of having to adjust and readjust my bra several times throughout the day to ease the irritation, they even became noticably swollen with the tell-tale sign of darkness around my nipples. Every sign of early pregnancy that I'd had with my first child. By the third week of having these symptoms I was completely convinced that I was pregnant even though it was too early to test. I was shocked when my period came around the time it was expected - but I accepted that I must have SOMEHOW been mistaken about being pregnant. Then, after two days, it stopped. I know that it was heavier and brighter than "implantation bleeding" but definitely nothing like the normal heavy, six day flow of my normal period.
If I were trying to concieve and just hoping to be pregnant than I would brush my mistake off of wishful thinking -- but my husband and I were not trying to conciece at all; the symptoms were actually physically there and too prominent to ignore. I want some kind of explanation for what those symptoms were if they weren't pregnancy.