What happened in March could have been your body preparing months in advance.
When I first got my period, I had very light bleeding, then missed it the next month, then got it again the month after that. Your body's just regulating itself, and will be for the first year.
What you described is how mine started also. It's totally normal. Don't be surprised if you don't have a regular schedule because the majority of girls take a while before they get on a more regular schedule. It could take a few years for it to get regular.