Please help

So I’m 17 and I’ve have my period for about 3 years now. Lately ive noticed that it is like 40-45 days in between each period. And normally I’m only like a day or 2 late but this month I’m 6 days late. There is no chance of me being pregnant due to being a virgin. But I do masterbate between 2-4 times a week. Is any of this normal? I’m getting worried that something is wrong but I don’t want to freak out and it be something simple.