Hi Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concern...
As you have started birth control 3 days ago, a
Plan B pill is not advised to prevent
pregnancy. Plan B pill may cause irregularity of period & is not advised to be taken along birth control or
contraceptive pills.
Your birth control pills should be able to prevent pregnancy. Your partner have also done withdrawal method to prevent pregnancy. Kindly continue taking the pills. I would also suggest you to take these pills at approximately same time of day to be more effective.
However, Withdrawal method alone without use of contraceptive pills is not safe method for preventing unwanted pregnancy & it has high failure rate.
There may be some pre-ejaculation before ejaculation & research shows that it may contain some sperms in it. There may be some sperms left over penis from previous ejaculation too.
Don't worry you would be fine
Hope this information helps.