Many women have shorter or even irregular cycles. Mine used to be 28 days, then switched to 25. No problem at all.
Mine are usually every 21-24 days around there and its a pain in the butt, but doctors say its ok to have periods a little closer together than every 28 days. Check your diet, your hormones, your stress levels, sleep patterns, etc. It can be anything or nothing at all.
That's not too bad, about 24 or 25 days this month, right? The month before was longer than 28. Mine is like that alot, it's never exactly 28 days long.