Don't know if this is possible...

Question, I had unprotected sex on 11/14/15 with an IUD still in place, took a Plan b just in case on the morning of 11/16/15,less than 72 hours after the unprotected sex, I had my IUD removed 5 days after the unprotected sex on 11/18/15. I bleed pretty steadily starting on 11/20/15 until the 26th-27th. My husband and I started trying to conceive right away and I am now 6 weeks pregnant. Is it even possible that I could have gotten pregnant from that unprotected sex 5 days before removal even with plan B and full cycle, pregnancy tests were also negative 4 weeks after that unprotected sex so I don't think it's possible but wasn't sure. TIA!!!