Iud/Am I pregnant (Tmi)

So I got an IUD on the 6th and my boyfriend and I had sex yesterday and he came inside me a little bit yesterday? And I have my string check on the 20th. I heard there is a slight percentage of women who can get pregnant on the IUD. Should I talk to my doctor or wait to see if I get symptoms later if I do. And what is the proper terms to use while I talk to the doctor. Idk I know it's hard to get pregnant on an iud but should I tell my doctor what happened?