Thats crazy! Im 24 and i have NEVER missed a period since i was 18. Soooo! My doc wont see me anymore they gave me one blood test and it said neg and they said there wasnt anything they could do. Im bloated and my nipples hurt sooo bad i can barely shower. I didnt have sex for 2 years and then may 23 i got married and havent had a period since. Im going crazy!
i am now 2 months late got 2 neg and the doctors hav'nt got a clue and won'nt run anymore tests they did blood test and they were ok and my periods run on time
I would wait a couple more days and then take another pregnancy test(unless period comes), and take it first thing in the morning to ensure the most accurate results. If you still get a negative and do not get your period go and get a blood pregnancy test from the doc.
oh and the chances of pregnancy after a vasectomy are 1 in 4000, or 0.025%...so it's a very very slim chance.
When I was younger I never knew when to expect my periods, they were so irregular. When they did come they were most painful with enormous clots the size of an egg. I had one miscarriage when my cervix refused to close. I have more recently found out that I have an autoimmuine disease which could have affected this. You could get yourself checked out (for Hughes syndrome/APS. They only discoverd it a few years ago). Hope this is helpful.