Independant Contractor Tax Question?

i work as an independant contractor at a medical clinic; they take nothing out of my check. i make $360 dollars a week (or $1440 a month); ive worked here for about four months now and am wondering whether or not i need to file taxes yet? ive been putting money aside so itll be there when i do (pay taxes). how much do you think ill be taxed when my marital status is single, and i have no dependents?