i had protected sex on October 12th, 2015. i got my period on the 14th lasted till the 18th of October. when November hit my cycle wad 40 days till i got my period. i was never late. i did do a pregnancy test on nobember 15th, it came out negative but my period was still a no show, i was so stressed and worried. lets not forget i am 15. i did another test a few days later and still negative. but still no show. so i waited and tried to calm down and got my period on november 22nd and it lasted to thanksgiving. in my mind i was happy but still worried and was waiting till december to see if ill get my period that month. when december came i waited. {i just thought last month was me over stressing and thats why it came super late} so in december it was the 4th week. i always get my period on the 4th week and when i didnt . i was confuse but i wasnt trying to over think it because i had protected sex and had 2 periods after having sex so i just waited. than i got my period on december 29th 2015 and it lasted till the january 2nd. my question is, why is my cycle longer now? and should i be worried about being pregnant? should i take an another pregnancy test?