You may have an infection. Do you have any abdominal pain?
Or alternatively, if you are sexually active (and this occurs after activity) you may have torn a bit. Being torn resolves with time, but in the event of an infection it is important to try and see a doctor if it's at all possible so you can get treated for it. Untreated infections can get really nasty.
Cranberry juice is pretty effective for helping clear up infections like the poster above me mentioned (good advice) but there is no substitute for seeing a doctor and getting antibiotics.
I agree that this sounds like a Urinary Tract Infection (UTI). These are very easy to get. You can get them from sex, yes, but you can also get them even from holding it too long when you need to urintate. I have had them a couple of times and they are no fun!
I suggest drinking plenty of water and cranberry juice, or water with some cranberry pills (you can buy these in the vitamin section of stores for less than $10). If you do this early on, you might be able to flush out the bacteria and avoid the infection. Unfortunately this might not work and you may need antibiotics. This WOULD require a doctor's visit. I know you said you can't go to one, but if it's an infection that sticks around, it can possibly spread to your kidneys if not treated, so it's very important. If it's a money issue with the doctor, they can usually set up payment plans to make things easier for you. When you get the antibiotics, the infection typically clears up in about a week. You will start to feel better after one to a few days, but it's important to continue to take the medication as prescribed.
For relief with the burning and pain, you can take AZO pills, which are over the counter at pharmacies. Keep in mind that these will ONLY help with symptoms and will NOT cure an infection. Also, they do change the color of your urine to orange, so do not be alarmed, as this is completely normal.
If it's not a UTI, do you think you might be dehydrated? Do you drink a lot of sodas and acidic beverages? I have known people who had burning while urinating simply because they needed to drink more water. With a UTI, you usually will have to urinate more often, might feel bloated or have some pain in your lower belly area, and the pain/burning typically gets worse as the days go on. Sometimes you might notice blood in your urine, although this does not happen with everyone. With me, I find that my symptoms are just annoying at first and I need to use the restroom very often, although there is very little urine. Then I start to notice sharper pains within a day, and if several days go by before I can get to the doctor, I notice small bits of blood and the pains get sharper. Some people's symptoms are different though!