Estimated tax for independent contractor?

I have been an independent contractor for the past several years (averaging between 35-39k AGI). Every year, I send my taxes in by April (paid in full) and have never had any problems or penalties. The company I work for never withholds anything so it has been pretty much left up to me. I recently read that I am supposed to send in quarterly estimated tax payments every year! I have always used TurboTax for Business to prepare my returns and when I turned in last year's taxes it stated that estimated taxes were recommended but not required (as I generally preferred to make one lump payment versus four smaller ones, I did not choose this "option" ). Yet I recently stumbled upon evidence to the contrary on the IRS website. Now I found out that not paying estimated taxes and paying it the way I do is "illegal" and I could incur all sorts of fees (past and present). I am also a full-time student, so obviously I don't want to have any problems with the feds. What should I do? Should I pay my taxes like always this time around and start paying quarterly in April (for the first installment) for next year's, or will that make things even worse? Thanks!