Need some advice..

I gave birth 7 weeks ago, I'm supposed to get the copper coil fitted tomorrow.. here's the thing.. a week ago, SO and I had sex, the condom snapped half way but we noticed and replaced it before he finished. Two days later I noticed I had fertile CM so of course, now I'm worried that I may be pregnant again and going to get a coil fitted. I know the chances are super slim that I am pregnant, I don't know if I should cancel my appointment tomorrow and wait til I know for sure I'm not pregnant again. If I do get the coil fitted and I am pregnant, will it affect anything? Could I still go on to have a healthy pregnancy/baby?