Definitely get the help of a disability lawyer to help you win your case. I just recently read that approximately 70-80% of all disability claims are denied the first time around and out of those who are denied, about 1/2 of them don't pursue things further.
I know getting your disability won't help right now - as it is a long process - average 18-24 months - but it certainly is worth pursuing.
The more documentation (test results, MRI's, CT scans, Xrays, doctor reports, surgery reports, etc.) you can provide with your application, the better off you're going to be. And if you can get your doctor to write a letter stating that he/she says that you cannot work due to your medical condition/s, that will help also.
As stated by one of the posters above, there are many disability law groups who do not charge any upfront out of pocket fees. They get paid a percentage of whatever back pay you are awarded by Social Security only if you win your case. If you don't win, you don't owe anything. I, personally, used Binder & Binder, and was very pleased with their work. The other benefit of using a law group such as them (or others like them) - in addition to not having any out of pocket expenses - is that they also do majority of the paperwork and telephone/leg work for your claim. This is their job - they are used to dealing with all the hassles of paperwork, etc., taht Social Security requires - so that is one less worry on your shoulders.
Know that you are not alone - the people here on medhelp are great. If you ever need/want someone to talk to, vent to, yell at, etc. - please feel free to send me a message. I'm not a single parent like you are, but I sure do know how frustrating it is living with chronic pain.
Have you gotten a lawyer, I would keep trying, make sure your doctor documents in your records that you are not able to work. Don't give up!
Call Heard Law Firm. Have you filed for disability yet. If you have not, they will do it for you at no cost and will only take their fees out of back pay you are owed if you win.