Can't find strings?

I'm in my second month of having my Skyla IUD. I'd only checked once before and I found the strings but they were really hard to feel. Went back for an ultrasound about two weeks ago and everything was in the right place. Now I just checked the strings again after having unprotected sex twice, and I can't find the strings. I leave for college in a day and can't get to the gynecologist to check. What should I do?