It’s normal. Periods are weird and if your second one didn’t come just after the first one ended, or you are experiencing severe bleeding or pain, you are good. I myself have a really unpredictable cycle, it’s definitely not regular and it suprises me every time. Sometimes it’s longer sometimes it’s very short. It’s what periods are here for, to be a pain in the ass 
. But if you are still concerned you can always go to get a professional opinion from a gynaecologist 
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