Hello
I appreciate your concern.
Since pregnancy test is negative and pelvic
ultrasound is also normal so you need not to worry at all.
Delay in periods might be related to number of reasons like Hormonal imbalances, stress and anxiety, diet and infection or inflammation of the Genitourinary tract.
I would advise you for a battery of investigation like CBC, ESR, blood sugar, urine culture and hormonal study to establish a diagnosis.
Bloating might be related to
indigestion, Dyspepsia and
acid peptic disease, so I would advise to take antiacidity medicine like
pantoprazole or
ranitidine group of drugs with antacids for 4-5days.
You should avoid fatty fried spicy and junk food and carbonated beverages.
Hope you will find my answer informative and useful please feel free to ask for follow up question I will be happy to help you.
Best wishes