I don’t know what’s wrong with my body.

I haven’t had my period in almost a month. (I took plan B like more than a month ago) I have taken 4 pregnancy tests and they all say Negative. Everyone at home all know when I have my period because I cramp for all 5 days and it feels like I’m always about to die. Now my mom is asking me if I’m pregnant and I told her know. I have half a mind to show her my pregnancy tests but my sister said I shouldn’t because she’ll be like so you thought you were pregnant that’s why you took so many tests. My sister said I should take it with food coloring till I actually see it and I have half a mind to do that. I don’t know what to do