Yep, it's very common, especially if you don't have a heavy flow for 'brown discharge' to show up.
Actually that's just what blood looks like after a while; the iron in the period oxidises and results in the brownish colour.
Lots of people also have a varied or inconsistent periods and it isn't a problem. I'd guess that as you're only a few months in it might take a while to work out what the routine is for your body and your cycle. You might actually start noticing patterns or the irregularity might settle into a more regular groove, or not. Either way there isn't one 'normal'.
Have you recorded any dates of when different parts of your cycle happened? Keeping a diary of such things can be a really useful way to start noticing what is going on!
"In between two tall mountains there's a place they call lonesome.
Don't see why they call it lonesome.
I'm never lonesome when I go there." Connie Converse - Talkin' Like You