Why does my iguana always poop on me when i hold her?

i have had her for about 10 months. at first she wouldn't poop on me when i held her but now she wont stop. it has gotten to the point where she has been in her tank for a whole week and i wouldn't hold her. i told my mom i wanted to take her to the pet store but then i thought about it and decided against it. i do not know if my iguana is a boy or a girl but i just gave her a girl name. anyway why does she poop on me and how can i get her to stop.