Hi,
The burning sensations and pain you've described around your vulva (external genital organs) can be caused by various conditions, such as: vaginitis, a yeast infection, bacterial vaginosis (BV), or a possible sperm allergy, etc... To figure out exactly what is causing your pain and burning sensations, you would have to be examined by a medical professional, in person. Try using an over-the-counter pain med., along with lubricant, and a condom the next time you have sex ~ just to see if this makes any difference.
My next suggestion would be doing some online research about local or nearby health centers and clinics in your area that offer free or low payment services for women. Planned Parenthood and other health centers offer very affordable gynecological care, that you don't need insurance for. You can call ahead to find out more information about costs and services.
Hope you feel better soon :)