Insurance woes

My insurance woes have started again. My job won't insure me until I provide proof of a start and end date from my previous insurance company, which I didn't realize until I received something from them saying I was denied coverage for a year or until I provide this. This will mean actually finding the letter or getting my old insurance company to send a new one. Last week, the fall-back insurance company that my parents forced me to enroll with sent me a letter saying that I haven't paid my bill so my coverage has been terminated. What bill?! I never received a bill! Having had 5 different mailing addresses in the past 3 months it must have somehow not been sent to the right one. This wouldn't worry me, except I am receiving bills for thousands of dollars from my trip to the hospital and subsequent examination and when I should have two means of coverage I actually have none. I'm pretty sure that this will all be resolved, but I'm still a little worried.