Why Am I getting a decrease every time I put my second W-2 and my tax refund

[elc41]

because you are adding income and have most likely used up all of your deductions and credits or have not yet put them in. The extra income may also have raised your tax rate. You really  need to enter everything before you get the exact picture

[macuser_22 · Accepted solution]

Each employer withholds as if that was the only income, but when added together you can move into a higher tax bracket so more withholding (or paying estimated tax) is necessary. When two or more jobs you might need to claim single or even have an addition amount withheld. This is very common with two incomes.

See this FAQ:
Why did my refund drop when I entered another W-2?
https://ttlc.intuit.com/replies/3798403