Consdering PMS?

I have my PMS regularly each month, but for the past two months it's been going off a bit. Is that okay? For example:

In October: It was normal.
In November: It started 2-3 days later than usual.
In December: It started 4 days later.
And now: I'm waiting, it's been like 3 days later.

Can someone please help me?
Well if you are younger, your periods usually don't have a set flow to them yet. I think it's around 19 or 20 when periods start having a set date. I'm pretty sure you don't have anything to worry about, just make sure you let your gyno know about anything unusual, and take visits regularly.

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