Can't feel the strings..help!!

So I've had my Mirena for almost a month now. I try to feel for the strings but I can't feel anything. My boyfriend says he does but I can't. Another thing how do i tell if it's out of place? I've been having cramping a lot lately and I'm also worried that I could be pregnant. My boyfriend has finished in me since I've gotten in. I got it inserted a day after I started my period. I've been constipated and extremely moody. My sex drive is very low as well and there's a strange smell down there that I have never had before.