Severe Lower Back Pain

Patient: I am wondering if I have a pinched nerve, pulled muscle, or something else? How to treat?

Symptoms: I have had sever lower back pain (only on the left side) for months now. I take Ibuprofen to reduce the pain. The pain is constant when the medication wears off. I try to bend at work so that my back wont hurt, but now I feel like I am injuring my knees. I am a female, 5’8″, 260 lbs.
I realize I am over weight, and that is why the pressure on my knees are becoming an issue, but I cannot find a way to get rid of this back pain. I have done stretches, rested, ignored it, massaged it, medicated it. I am at my wits end. I can’t afford to go to the doctor, but I’ve been saving up, so if you could help that would be awesome.