Can i collect employment while working as a private contractor?

ok well i lost my in dec.09 and received my 1st employment check i think on christmas day and ever since than i have been collecting employment,and well i work as a caregiver now starting since that last week of dec.09 but my company does not take out taxs out of my check,i work basically as a private contractor and i have to file my own taxs. Well my job doesnt always get me work,it depends on my clients that i have. Well what i wanna know is can i get in serious trouble for collecting employment and not report what i make from my caregiving job. My tax preparer told me that the 1st $2400 from employment is non-taxable which to me means free but everytime that i have received employment i have been taking out 10% of taxs out of the employment check. Well i called another tax preparer and they said that whatever how much i have received in employment to subtract $2400 from whatever i have gotten,i might be over let say $500 dollars and thats what i would have to probably pay back to employment..Can anyone help me with this issue..thanks