First of all, you should repeat the blood test
for beta hcg (as early test may give negative result) & USG lower abdomen to confirm/ exclude intrauterine pregnancy
In exclusion of pregnancy, other reasons are ovarian cyst
imbalance, stress/ anxiety, thyroid problem, wt gain/extreme loss, irregular eating habits etc. Increased cervical mucus is commonly seen prior to starting of period. If there is no itching/ bad smell, then you have nothing to worry.
Do some investigations to rule out underlying pathology like Thyroid profile, blood sugar & other hormone assay etc. So consult with your doctor and take suggestive measures.
Avoid stress/ anxiety by regular deep breathing or yoga, take healthy diet with iron supplements
, control body wt and maintain genital hygiene properly.
If you need further consultation with me, then you can visit http://www.healthcaremagic.com/doctors/dr-soumen-patra/63326.
Take care yourself.