firstly relax and dont worry..as u said ur preg test is negative 4 times ..and ur not getting periods for the first time..
i suggest u to take hormonal
tablets for three cycles to regularise ur dates as it might b hormonal disturbance and even any mental stress
ur going throoough,,i hope u even developed gastritis
due to irregular diet or stress and hence u feel your stomach swollen up..
and i even suggest u to get you thyroid
profile done and know ur thyroid status..and also get your Hb percentage done too..
take good diet and have good tension free lifestyle to develop you hormonal levels to normalcy..
all the best ..