If you have Self employed income from working ( not rental income that is reported on the Sch E) then you do need to file a Sch C.
If you have net self employment income of $400 or more you have to file a schedule C in your personal 1040 return for self employment business income. You may get a 1099-Misc for some of your income but you need to report all your income. So you need to keep your own good records. Here is some reading material……
IRS information on Self Employment….
Publication 334, Tax Guide for Small Business
Publication 535 Business Expenses