i took a pregnancy test back in january

I am 15 years old yeah that souds bad but that just shows i will tell you anything to get you to tell me whats wrong... Lately i have been very tired ill go to sleep around 12 noon thinking i will wake up in 30 minutes or so but dont wake up for hours. i have missed 4 periods...my last period lasted in 3 weeks...my eating has changed and i feel dizzy sometimes to... i took a pregnancy test back in january but i dont feel its necessary now since its been about 5 months since i have had sexual intercouse....please if anyone knows whats wrong or if anythins serious please get back to me...and major heads have happened and i was put on pain pills....but i havent taken one....could i be pregnant or something?
protected sex...