Your query is appreciated.
There are various causes of amenorrhoea ( absence of periods ) apart from pregnancy
Firstly, you need to consult a gynecologist to confirm that you are really not pregnant, as home tests are not 100 % reliable.
Secondly, you have mentioned that you are overweight
Obesity also leads to menstrual irregularities.
You have not mentioned your age.
If you are peri menopausal, such menstrual delays are also to be expected.
imbalances such as thyroid
adrenal disorders or sugar imbalances might contribute to your problems.
If you have a history of multiple abortions and surgical terminations, the uterine lining might be thinned out and you might have this problem.
There is an entity called premature ovarian failure
wherein the periods stop earlier than usual for a woman's age.
You must consult a practitioner at the earliest, and get your various tests and investigations as suggested above by me, in addition to a pelvic examination to know the cause of your amenorrhoea.
Meanwhile, weight reduction, moderate and regular exercise and a healthy diet will certainly contribute to your well being.
Hope this helped you.