The symptoms you are feeling could be due to gastritis
as well as a delayed period. You may repeat the HPT and if still negative, go for a blood test
followed by a sonogram, preferably a trans-vaginal ultrasound
. You need a proper complete couple work up if you have not conceived, to locate the cause and plan the treatment strategy. You may also need treatment for your gastro-intestinal problem. Consult your doctor for further advice. Take care.