Hello..
Upt may be false negative also if you are sure about the intercourse..secondly you can get a scan done which will help us rule out pregnancy or any other conditions like pcos, any other cysts etc...are you overweight? Sudden body hair growth? .
Apart from this sometimes due to stress,tension also there might be delay in periods,
thyroid status..all these factors come into play...just conuslt an gynecologist in person