Missed period. When does pregnancy symptoms start to show?

Since your boyfriend had a vasectomy and you have taken Plan B, it is highly unlikely that you are pregnant. Your period probably hasn't come because you are worried about being pregnant, and the stress of it all is causing it to come late. Mine comes late when I have times of extreme stress as well. Plan B can cause your period to come late and the symptoms you are experiencing are similar to stress symptoms. If you are still really worried, though, talk to your doctor and/or a gynecologist and they should be able to clear your pregnancy worries.