Skyla and sex

Okay so I have had the skyla for a little over a year and I have always made my boyfriend pull out... After seeing that most women let their men finish inside of them I decided I wanted to try it! He did it four days after I was supposed to be out of my fertile window. I have been cramping and pmsing and I feel like I'm going to get my period but I'm just so nervous! I'm supposed to start tomorrow. Do you think I'm okay to let him finish inside of me?