Your 2 preg card test is negative.
Method of doing the test is very important.
Have you interpretated after 20min?
Single control line appeared?
Usualy these tests are well sensitive & specific.so if it was done properly then chance of pregnancy
2&1/2months of secondary amenorrhoea(no period after menarche
) may be due to various reason excluding pregnancy(it is most common cause).
Others may be anovulation
To know other reason you should mention your weight,height,medications you take,other diseases.
So it need your examination and need some investigations.
consult a gynaecologist.
Best of luck.