Pregnant on nexplanon?

So i have the nexplanon for about 6 months, i never missed a period on it, if anything it made my period longer. So i had intercourse back in November and this is what my tracking calendar looks like back in November . Red highlight is my period and the blue is ovulation. The hearts mean sex so on the 18th and 28th i had intercourse. Then that week I remember experiencing like lower back pain, spotting (i never spot) I remember one day i wiped and seen light pink (which i never got close to end or before period), i also remember being very nauseated. so i decided to take sum pregnancy test they came back negative. I figured nk biggie ill be getting my birth control removed dec 15 which happened and still no period. So fast forward now i still have no period which makes me about 33 days late and lately i just been having sore nipples.