Go to the dr. ASAP! I just went thru this! I had my miscarriage and had normal periods also...just like you!! But, I kept testing positive w/ a blood test by the doctors and it turns out I needed a D&C because some of the tissue and placenta was still in my uterus!! My HCG levels stayed around...
When I was pregnant w/ my daughter and I went to take my 1 hour test, I was just told not to eat pasta the night before and that I couldn't eat 12 hours prior to the test! That's all they told me and my tests came out fine! I don't know why they told you what you could and couldn't eat 3 days...