Period 20 Days Apart

My periods were every 21 days for awhile and my ob said it was still normal. I had a very short luteal phase though and that caused some problems getting pregnant. If you are trying to get pregnant, then you may want to consider some extra B6 to extend your cycle. Talk with your doc. Most docs will suggest going on the pill for awhile to get your sysle regulated and that was something I did not want to do ( I do not react well to hormonal birth control) so I opted just to eat healthy and exercise and take some B6. It did help and I am preggo with #2 now. Of course every case is different so you should see your doc and if you have no issues with the pill, then I would suggest that as an option for you. All the best!

Have you recently been on Birth control?
Sometimes your body resets itself and can bring on "extra" or late periods.

Could you have been pregnant? Your body would go thru cramping and bleeding if it was not a viable pregnancy also...

If it continues to be close together or oddly irregular then I would see the DR about it...

Are you under a large amount of stress, or have entered an new or unknown situation? A lot of people don't get periods, if they are stressed out. I am the opposite. I get periods close together, if I am under stress.

I have always been that way and have never been on birth control

I have always had 20-24 day cycles my entire life, since I first got my period as a teenager, except when I was taking the pill which controlled it and forced it to be 28 days. It is super rare to even go 27 days for me. I only go that long when I've been sick or stressed out. The "standard" 28 day text book period is just an average. A number to give the medical profession something to work off of. Not everyone ovulates on day 14 and has a period at 28 days. Same as not all babies are born at 40 weeks. I ovulate around day 10 on average but I know I can ovulate as early as day 6. I did when I got pregnant with my daughter ;)
I was told by my midwife that it's fine and normal. It also does nothing to prevent you from getting pregnant, I've got 3 kids :)