I Had Sex On 9th And 17th March. I Missed

I had sex on 9th and 17th March. I missed my periods in April which were expected on 6th April. I haven't got my periods yet. I did 2 pregnancy tests but both came to be negative. I am having abdominal pain intermittently and had vomiting once. Does this indicate a pregnancy? Can it be an ectopic pregnancy or something? Or is it just because of stress?