Anything I can do after 4 days of unprotected sex?

I had sex using the withdrawal method 4 days ago during my fertile window. Is there anything I can do at this point to prevent pregnancy caused from possible "precum"? Would the plan b pill still work after the 72hr window? Also, how long do I have to wait to take a blood pregnancy test? (I go to see a doctor in a few days for a checkup anyways).
All info will help. Thank you! 

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