Period

Namine

Its been 39 days since my last period and im 12 days late. Should i be worried? Btw im 15

Edit: i had sex on the 31st and my period started the 12th of January but hasn't come at all this month. My friend made me an appoinment for the 22nd of this month which is on Wednesday but im still pretty freaked out because it's been so long, if the test comes back negative. Whats wrong with me..?