It's always worth going back to your W-2s to review your entries. Most common errors are decimal point and comma errors.
It's not unusual, though, for a married couple to end up owing. Payroll tax tables would assume that you each receive a standard deduction or married filing jointly. That amount is now up to $12,700. When you actually file, though, you only receive that deduction once on your joint return, not twice. Taxes are also withheld just for the tax rate on the income on that W-2. When you file, though, the tax rate is determined by your combined income.
For example, only 10% of your income up to $18,650 is withheld. When you combine your incomes, you only get that 10% rate once, pushing more of your income into the next bracket.
Most married couples do best to claim one person as married but withhold at the single rate. That's a request you make on a W-4 for your employer.
It would be unlikely for you to do better by filing separately because you lose many credits and the tax rate is higher.
