Thanks for writing to DoctorSpring.com with your health concern.
Sometimes, there is a rare possibility of an ectopic pregnancy ( pregnancy outside the uterus ) or a miscarriage, in which case, the home pregnancy test would not always be reliable.
It is better to rule out these possibilities with a blood B HCG estimation, which will reassure you, particularly as you are having some symptoms too suggestive of a pregnancy.
If the B HCG is negative, then please go for a complete gynecological examination ( per vaginum and per speculum ).
Also a pelvic transvaginal ultrasound scan, and hormonal levels - FSH, LH, TSH, Prolactin, OGTT, DHEAS, Free Testosterone.
That will rule out hypothyroidism, PCOS ( polycystic ovarian syndrome ) and endometrial hyperplasia or a polyp / fibroid which can cause such spotting.
ALso, stress, anxiety, weight gain, excessive smoking or drinking, travelling, late nights, erratic diet, ingestion of hormonal medication - all these can replace your normal period with spotting.
All the best
Please feel free to discuss further.