Depending on which test you use, you may be able to tell if you are pregnant in as little as a week after ovulation. A blood test is the earliest test to show a positive result (7-11 days after ovulation), while some home pregnancy test kits can test positive at the time of your missed period (14 days after ovulation) in up to 95% of pregnant women. If your last period was more than seven weeks ago and all tests since then have been negative, then it is unlikely that you are pregnant. But, it is difficult to say for sure without knowing the length of your usual cycles (the number of days from the first day of one period to the first day of the next).
With this information, if you still think that you might be pregnant, you should ask specifically which vaccinations you need. Some vaccinations (e.g. the flu shot) are safe during all trimesters of pregnancy. In fact, it is recommended that all pregnant women and women who plan on being pregnant during flu season (October through May) receive the inactivated flu vaccination. Other vaccinations such as the rubella vaccination should not be given during pregnancy. The rubella vaccination is what we call a live attenuated vaccine, meaning it consists of live but weakened virus. If you receive this vaccination during pregnancy, it can theoretically cross the placenta and affect the fetus although there have been no reports of adverse fetal effect in women who were inadvertently vaccinated during the first trimester. For more information, visit the CDC’s website. It’s a great resource with information about vaccination during pregnancy.