First of all, I suggest you to repeat the blood test
for beta hCG to confirm or exclude intrauterine pregnancy
as early pregnancy test is less significant.
If you get NEGATIVE result again, then other reasons of spotting like hormonal
imbalance, stress/ anxiety, thyroid problem, wt gain/ extreme loss, irregular eating habits etc. are needed to be ruled out properly.
Here you need some investigation to rule out underlying pathology like Thyroid profile, LH/ FSH, Blood estrogen & progesterone
level etc. So consult with your doctor and take suggestive measures.
Avoid stress, take healthy diet, control body wt and need proper sleep. Use tight breast support for discomfort & ispaghula husk with water at bed time to get relief from constipation