Iv have had a baby I had bleeding for 3 days when I fell pregnate with her it felt exactly like a period cramps sore boobs, bleeding was the same ..so you can bleed nd think you might have your period but you can't have a period there 2 diff things..! If I was you I would go get a test or go see a doctor :)
Periods can last for 2-7 days and if you bleed for 3 days instead of 5 days then it dose not indicate pregnancy because 3 days periods are also normal. Periods start when brain detects that pregnancy has not taken place. This condition result in withdrawal of hormonal support for uterus and result is menstrual bleeding. So, periods means no pregnancy. In my opinion, you are not pregnant but satisfy yourself by taking pregnancy test.
THere is no reason to think you are pregnant if that is your only reason for asking. Periods are often a day or two longer or shorter, especially in younger women, and if your period was otherwise normal then you weren't pregnant at that time. Any time you think you may be pregnant, you could have a look at a list of pregnancy signs to help you check.