Am i a complicated wreck? whats wrong here?

my sister and friends tell me i worry too much. i dont think i do i think my worries are justified. ie; 10 yrs. ago i had thyroid ca and had the rx for it and things have been fine. recently after a routine blood check my dr said my levels have changed and are slightly elevated. i had a neck ultrasound and it was negative. now she wants to to a total body scan (i have to drink radioactive isotopes) she said "i dont want you to think its an emergency but i think since the #s have changed we should do the scan to put both our minds at ease, with your neative neck ultrasounds i dont expect we will see anything problematic." NOW- this is where my problem is; when i was first dx with thyroid ca the dr had found a nodule and said"dont worry 95% of them are benign on biopsy" so i didnt worry .2 days later i got a call "you have thyroid ca." well i was in the 5%! So now , when someone says dont worry theres just a small chance or its probably ok, i don't believe it,i worry (alot)! i get all tense and distracted mainly because i am the sole provider caretaker of 2 small children that i love . if something happens to me (i worry about this all the time!!) then they will go to their totally disinterested foreign father who will probably take them to his culture where they will be terrified! am i wrong to worry about this?