Grr, I hate that. Mine has just started 2 weeks early for no apparent reason. It could be normal for you though, having an irregular cycle. Mine was until I started the pill, and even then it took a few different brands to find one that regulated it.
Cysts aren't uncommon either, and are rarely dangerous, I know it sucks but I'm sure you will be fine
I can understand how going through all of this would stress you out though. If you find yourself dwelling on it then distract yourself? You can't do much about it at the moment so thinking about it might just make you feel worse.
Im sorry you are going through this, I can't imagine what it must be like. Good luck with it, Im thinking of you!