well, let me tell u something it is not bad thing and u are not in trouble in a short run like somebody earlier said that u could even file ur tas return which u can. but, talking about long run, if u are to apply a green card through h1 which will take almost 3-5 years upon ur change of status to h1 it will really difficult to get green card. ins wont do anything if u have worked less than 9 months on cheque while being on f1 status but if it is more than that u can work as long as us company gives u job but once u are ready to apply for ur green card problem starts there. i don't know how long u've been working on cheque but try not to work for more than 9 months if possible. because we all have problem being student and i know sometime u have to do whatever uhave to do to live here.