You might be illegally classified as an independent contractor if you work for one employer and get paid a salary. But that's a problem for another day.
Next year you'll know better than to wait for the last minute.
L-1 is right. You might have a bunch of business deductions available to you for which you can file an amended return as soon as you figure it out.
Start by studying IRS Publication 334 Tax Guide for Small Businesses.
https://www.irs.gov/pub/irs-pdf/p334.pdf
Then look at Schedule C and it's instruction booklet:
https://www.irs.gov/pub/irs-pdf/f1040sc.pdf
https://www.irs.gov/pub/irs-pdf/i1040sc.pdf
Self employment tax:
https://www.irs.gov/pub/irs-pdf/f1040sse.pdf
https://www.irs.gov/pub/irs-pdf/i1040sse.pdf
Once you have read all that stuff you would be wise to hire a tax pro to thoroughly review your business paperwork and create your amended return. If you are lucky you might cut that tax bill in half.
Not if you pay quarterly estimated taxes.
https://www.irs.gov/pub/irs-pdf/f1040es.pdf
Your first quarterly payment is due today so you're already in the penalty phase so I suggest you get to work on figuring out how much you need to send every quarter and then just bite the bullet and do it. Otherwise you'll really be in a bind next year.
If you think your tax bill is going to be $10,000 next year then you need to send $2500 each quarter. Though I suggest doing your amended return for 2016 ASAP as it might be a lot less.

