I had sex on the 16th with my girlfriend. she took plan b on the 18th. when should we expect her period to come? when should we try a pregnancy test?

Plan B: First it is important to understand that Plan B typically works within the first 72 hours after have unprotected sex. Her period shouldn't have changed much, she should still expect to have her period around the same time as any other month. You can take that pregnancy test now if you would like.

variable: Depending on the time in her cycle, it is variable as to when her menses will come. I recommend a pregnancy test 2 weeks after intercourse.