Should i file an itr ?

Should I file an ITR if I've taxable income from Short Term Capital Gains which is my ONLY source of income and it is very much below the basic exemption limit. Till now I never had any taxable income and so I never filed an ITR. And should I file an ITR If I have Short Term Capital Loss?? If I should file an ITR when I've STCL & if I don't file and ITR, what are the consequences I've to face??