Can you get pregnant with an iud in?

I have had an iud in for almost 2 years now. But lately I have been having pregnancy symptoms ( nausea, craving, rapid weight gain, back ache, fatigue). I have taken 2 pregnancy test which one came up invalid and the other one was negative. I have gained 10 lbs in under a month. I have never had this problem before except when i was pregnant with my first two. Is it possible that i could be again or is it something else??