No one on Answer Xchange can see your return. There are are lot of variables that affect your refund or tax due including how much you earned, how much tax you had withheld, your filing status, the number of dependents you claim, your deductions and credits, etc. You may have lost Earned Income Credit or the Child Tax Credit. Or do you have a healthcare penalty? The best way to find the difference is to print and compare 2016 and 2017 side by side
And of course, always check your own data entries, looking for errors such as misplaced decimals or extra zeros.