Pregnancy and iud help!

Ok so I went yesterday to the OB to have a blood test don’t to see if I’m pregnant because I took a test and it showed negative till it dried and then there was a very faint second line. If it comes back negative I want to get the iud put in, BUT this is the thing I’m curious about, me and my boyfriend had sex this weekend and he started cumming without knowing. I pointed out he was and he was like wth I’m not even close to getting off?! So I have no idea if any of it got in me or not. If it did and it took then it wouldn’t show up in a test, so my question is... if I get the iud put in and I am pregnant will it hurt the baby? Or will everything be fine? Please help with any information you have!!!