The only reason that you can not file tax returns for a given year is if your (worldwide) income for that year was below the filing threshold. The filing threshold for each year can be found by looking at each year's tax Form 1040 instructions, in a section near the beginning called "Who Must File".
If you did not file because you were not required to file because your income that year was below the threshold, then everything is fine. Per the I-864/I-864EZ instructions, in that case you would have to attach a statement explaining why you were not required to file.
If you did not file and your income was above the threshold, you should file the back taxes ASAP first.
What matters for determining sufficiency of the Affidavit of Support is your current income (i.e. salary of your current job). Since you say that you currently have a good job, that should be sufficient. Make sure to include an employer letter (if possible) and as many pay stubs as you can.