21 days late neg. pregnancy test

So In April beginning of the month I got off my birth control because I was bleeding too much & in may the beginning of month I got my period and it was regular 4 days like how it was before I got on the implant in my arm, so I thought everything was okay then I got my period again on like the 23rd or 22nd of may only for about 3-4 days and had regular period cramps and etc. but now it says my period is 21 days late I haven’t spotted a spot of blood in almost a month and a half and had 2 missed periods , I went to planned parenthood got a urine test & home test it was negative but I’ve been feeling sick and headaches I eat so much now and I threw up for no reason only one time. Someone help me out pls