What would be the reason for my period coming again so soon?

Actually, that's a 27 day cycle. So it's not really as soon as you may imagine. The average cycle is 28 days but every woman is different. Some women have 26 day cycles, others have 34 day cycles. And some (like me) have so many days between cycles we lose count. So when our bodies do what's normal for other women (but abnormal for us) it's a bit weird. I don't know your body and can't even begin to guess why your flow isn't exactly what you expect, but I wouldn't think you're pregnant based on having periods that start 27 days apart. If you're really worried, take a test.