Thought it was my time

My husband and I have been ttc for 3 months. I guess I just thought if you stopped taking your birth control you would get pregnant. That's what the doctor tells you anyway. Regardless, this last month I thought for sure it was my time. I took the ovulation tests and had sex when I should. A few days after ovulation I noticed a small amount of cramping and thought it was implantation. A week after ovulation, there was a slight pink when I wiped and continued to have minor cramps and my nipples are tender, which never happens to me. Now, I believe I have started my period a few days earlier than normal. I took a pregnancy test just to be sure and it came up negative. I'm so disappointed.