I'm a 23 year-old female with two children. I had unprotected sex 4 days before my ovulation day and on my ovulation day. He used the pull out method, but I know full well that it isn't effective. My period is regular so extremely easy to track so I'm guessing my ovulation day is too. I started spotting the night of my ovulation day, which is odd because I never spot in between periods. I took an ECP the day after at 5:00PM, but I'm worried that the spotting was implantation bleeding. Is it possible that implantation occurred 4-5 days after unprotected sex and the pill won't work? Or am I wrong to be so worried.

It is very possible. You see, it takes a few days, not hours, for the sperm to travel up the vaginal canal, through the uterus and Fallopian tubes to meet up with the egg near the ovary. Then it takes a few more days for the fertilized egg to travel back down through the Fallopian tube into the uterus where it implants.

The withdrawal method is the least reliable method of birth control.

When trying to conceive it is advised to begin having relations a few days prior to ovulation for best results.

As J_9 said, it's possible. It could also be a bit of spotting from the recent sex or due to ovulation itself. See what happens when you would normally expect your next period.

It is possible, and ovulation days while may be regular, may not be according to online charts or phone apps, unless you are testing, you really do not know ovulation dates.

Also the longer you wait to take the "morning after pill", the less effective it is, 24 hours less than 12 and so on. But even taken right after, it is never 100 percent effective.

So yes pregnancy is a option.