I had unprotected sex 3 days ago. this is day 4 and i'm seeing a doctor, will this help prevent pregnancy?

Seeing a doc?: What is the doctor doing? If you don't take the morning after pill within 5 days to prevent conception, ask about it. Also get checked for STD's. Practice safe sex from now on! See http://www.plannedparenthood.org/health-info/morning-after-pill-emergency-contraception

Pregnancy prevention: There are very few absolutes in life; however, this is one of them. You are already either pregnant or you're not! You're well past the point of "prevention" once you've had unprotected sex. At Day 4, the best diagnostic test to determine pregnancy is a blood sample to determine a quantative beta- HCG level. Only after this test can you and your physician sit and discuss the results & options.

Emergency Contracept: If you had unprotected sex 4 days ago, ou either are pregnant or are not pregnant. Discuss with your doctor, some emergency contraception can be used up until 5 days depending on where you are in cycle.

Yes. Time is vital.: On Day 4, there is no time to waste. If pregnancy is possible, a primary care doctor can prescribe Ella, (ulipristal acetate) which will still work on Days 4-5. Plan B may not work as well as Ella, (ulipristal acetate) on Days 4-5. Another good plan is an IUD, which can be placed by an Ob-Gyn doctor. An IUD prevents pregnancy and starts working now (plus avoids the need for future Plan B or Ella), and can be removed when no longer wanted.