Ok idk if I'm pregnant I'm 17 and need answers?

I asked like 2 months ago about it also but now I had a pierod in April for 1 day ever since then I have not had one I havnt been on birth controll for over a year and my cycle had got normal again I take the prego tests and they come out negative well if it's not that and I kno I donthave a Sti what is it then please help