Hello Ritu,
Thanks for writing to DoctorSpring.com with your health concern.
Yes, menstrual irregularities are associated with stress, tensions and antipsychiatric medications.
Regarding the B HCG, it can only indicate one of 2 things.
One is that you had a miscarriage ( a chemical pregnancy ) - you would soon bleed then.
Second that it is a pregnancy - intrauterine or extra uterine ( ectopic ).
Only serial B HCG measurements and repeat scanning would show which of these situations is present.
Please repeat the B HCG level again tomorrow and let me know.
All the best
Take care.