Why is my total income different from last years?

Without access to your tax return, it is impossible to determine.

Your AGI includes your wages, your investment income and other forms of income.

The taxable income reduces your AGI by deductions. This year, there are significant changes to the calculation of deductions and the elimination of personal exemptions. For example, itemized deductions for state/local taxes are capped at $10,000, job related expenses are gone, and property damage is limited to federally declared disaster areas.

For more information about the impact of the changes in the tax laws, follow this link:  

How Will Tax Reform Affect My 2018 Taxes