Deductions & credits

Hi 

I'm a bit confused here.

I'm a self-employed contractor, so I receive 1099-NEC form from the contractor company.

If I receive the social security benefits, this income will be included as my social security earnings, right? Is it what they call the Schedule C income? 

Now, this is my second question. If I start withdrawing some money from my 401k account regularly, it does add up to my gross income, but it's not part of my social security earnings, isn't it?