Well the first thing you should do is invest in a pregnancy test. Most will detect if you are pregnant the first day of a missed period....technically that time has passed so if you are pregnant it would show it. Walmart has some for about $3 and they work fine. I've used them the last three times I was pregnant and all detected the pregnancy the first week I missed my period.
And not to get your hopes up, but with my first child I had a very short period of about two days and it was very light. I typically have a heavy period for the first day or two and then the next three are light. At any rate, I believe I was already pregnant. My doctor never would take that date, but my daughter was 8 lbs 14 oz when she was born. My next daughter was only 7 lbs 3 oz. And my son was 8 lb 15oz. So I may have been or may not. Honestly though I was weirding out my husband at that point with my hysterical outbursts.....so I really think I was already pregnant.
Good luck and God Bless!!
PS Don't pay any attention to the poster that said you gave too much information about your flow....When discussing whether your pregnant or not it's normal to talk about your periods. And I don't know a single woman that can't talk comfortably about their period...I mean it's natural and I've personally been having them for over 25 years...I think I can talk about it. Now do I want to hear about bowel habits because you go everyday??? Not really. Then again, if you think you might have colon cancer it would be relevant. Just thought I would add my two cents to that comment.