thanks for your query.
If you took a home pregnancy
test , and it was negative, chances are you are mostly not pregnant.
Also, a vasectomy
is quite reliable, that too, after 4 years, but there is a very remote chance of failure of vasectomy leading to an inadvertent pregnancy.
Also, you should wait for a aweek more before repeating your pregnancy test.
All the symptoms you describe could be attritubed to pre menstrual symptoms also.
Just wait and watch.
Take a repeat test after a week.
If you fail to have your periods by then, please consult a gynecologist.