What is the possibility that I am pregnant with an IUD? How would I break the news to my parents? HELP!!!?!?!?

Okay so here is the scoop. When I was 14 I got pregnant with my daughter who is now 9months old. After having her I got the marina IUD. What are the chances that I could get pregnant with it? My period is 3 weeks and 4 days late and I was still getting it with the IUD and now its like no where to be seen. I've been having some lower back pain and on and off headaches lately. I've been feeling a little sick on and off every once in a while but nothing major like when I was pregnant before. For the past week I've been extremely tired but late with my teething daughter might have something to do with it. My fiance keeps telling me not to worry and I'm just getting my self all worked up (I think he's really just trying to reure himself). Anyway I haven't taken a pregnancy test I plan to later tonight. If it comes back positive how do I tell my parents I am pregnant again? I have a horrible relationship with my dad and my parents are very ist (they prefer boys over girls so they majorly favor my brother). My fiance's mother is more understandable and said if I were to get pregnant With the IUD then it was meant to happen. She had gotten pregnant twice while on the pill. So any suggestions on how to break the news? Have you gotten pregnant on using the marina IUD? What were your symptoms? Anything would help! *and I do not appreciate those who are going to dis a teen mom, I am still going to school and I have a part time job.*