motorola milestone 2 gmail problem


Hi there! I'm not sure if this is the right place to post my question(and if it's not, i'm sorry) but i could really use your help.
I have a motorola milestone 2 and a limited internet plan. The last few days I noticed that my phone keeps consuming data even though i don't use the internet at all.
And I guess that today I found out why: Gmail application keeps on staying open even though I end it from task manager every 2 minutes. Not even 'force close' from "manage applications" doesn't close it for real. Gmail still opens itself and consumes my data.
Does anyone know what can I do?? I can't uninstall it :(