I made less than $4,000, am a Full Time Student and my parents claim me

If you are asking if you need to file, see the attached screenshot.

If you make self-employed income for more than $400, you have to file. 

I made less than $4,000 and my parents claim me.  I was told that I could apply to get the taxes I paid back but the IRS rejected my submission because someone already claimed me

Be sure to indicate (in My Info) that someone else claimed you. Then resubmit.