Thanks for writing your consult at DoctorSpring.com.
Basically, home pregnancy tests are upto 97 % effective in diagnosing a pregnancy. So if they are negative, then you are mostly not pregnant.
All the symptoms you describe can be a part of the normal early pregnancy profile, but these are not specific or reliable for diagnosing a pregnancy.
To be 100 % sure, please take a blood pregnancy test / pelvic ultrasound scan. Apart from pregnancy, other reasons can cause a delayed period - stress, weight gain, hormonal medication, hypothyroidism, polycystic ovarian disease etc.
I would recommend a complete gynaecological examination. That should include an internal check up ( per vaginum and per speculum ). In addition, a blood pregnancy test should be done. If negative, a pelvic ultrasound scan and hormonal levels ( FSH, LH, TSH, Prolactin, OGTT, free testosterone, DHEAS, fasting serum insulin , lipid profile ) should be done.
All the best.
Please feel free to discuss further.