As you got NEGATIVE result for both urine & blood test
, then possibility of pregnancy is quite LESS or NIL.
Some other reasons need to be investigated besides pregnancy like hormonal
imbalance, irregular eating habit, stress/anxiety, ovarian cyst
, thyroid problem, psychological factors, over weight or extreme loss etc.
Do some initial investigation like USG lower abdomen,Thyroid profile, LH/FSH to rule out underlying pathology if any. After that, consult with your gynecologist & take suggestive measures.
Avoid stress, take healthy diet, control body wt, wear tight breast support, use some medication like anti spasmodic for cramp or Omeprazole
tab (PPI), maintain personal hygiene and need proper sleep. Be well.