If I have only received SSDi ($12,000) and was a full time student with loans and expenses of over $9,000 in 2019, should I file for a tax return now?

If social security is your only income, you are not required to file.  Without a taxable income, you will not qualify for an education tax break.  

If you are asking about the stimulus check, you do not need to file a return.  The IRS has your profile and information and will send you a check if you meet the requirements.  

@joeljr65

How old are you? Are you a dependent on someone else's taxes?

If you are a student, over age 23, and are not claimed as a dependent by someone else (e.g. your parent) you may be eligible for the up to $1000 refundable American Opportunity (tuition) Credit. That credit is not dependent on having either kids or earned income. You must be at least a half time undergraduate student and actually paid tuition. Tuition paid by loans counts as paid by you (since you have to pay that back, someday)