Should I take a plan b?

I'm four weeks and one day postpartum and in the heat of the moment had sex without a condom however he did pull out and TMI but I don't think any semen got in me because he pulled out a few seconds before he started to cum. Should I still take a plan b? I'm going to get an IUD inserted at my six week check up and we usually use condoms we were just stupid. I know apparently you're super fertile after birth sooo idk if I should be worried or not?