Second period this month or pregnant?

Hi, I wandered if anyone could help! I had a period at the start of the month, one week earlier than normal. It wasn't very heavy at the start but was towards the end. I then woke up yesterday to another, what I would call, period. It's not very heavy just small brown patch on my pad but red when I wipe. My period is normally very heavy, so this is all very unusual for me. I am also have very sharp pain in my lower stomach and on the right side of my stomach. Worse than I normally get. Anyone got any ideas? Thanks x