I am no doctor but it sounds like the same problem I have.
My pain is:
low back, left of spine
the pain worsens and spreads down left hip
the pain can become quite bad and go down leg and when it does it causes my leg to go out and I fall
I am a workers comp case so I don't have MD's that care much about my case, I do have a very kind, wonderful, loving, emthathetic chiropractor who is the first and only medical professional to care and understand my pain. She and my phsyical theripist said that I most likely have strained my Piriformis muscle. And that causes Piriformis syndrome.
Piriformis syndrome:This syndrome occurs when the piriformis irritates the sciatic nerve, which comes into the gluteal region beneath the muscle, causing pain in the buttocks and referred pain along the sciatic nerve.[1] This referred pain is known as "sciatica." 15% of the population has their sciatic nerve coursing through the piriformis muscle. This subgroup of the population is predisposed to developing sciatica.
For me the pain worsened in the same way yours did. And has continued to worsen over the past 15 months. My case is different I was hurt lifting a 300lbs resident of the nursing home I worked for. He had fallen and myself and another cna had to lift him from the floor to the bed. I pulled every muscle in my back. I hurt the muscles so bad that the scar tissue that resalted when I tore the muscles causes me sever pain every day. So your pain may not last as long as mine or worsten to the level mine has.
I don't know if this is what you have going on but how you described the pain sounded like my pain.
I'm on workers comp and I've noticed that people with my type of injury (one you can't see on an MRI or X-Ray) don't get treated as well as people with injuries that can be seen or that have their own health insurence. no one has treated me for this problem, other than stretches my PT gave me or spinal manipulation my Chiropractor did (both helped somewhat). So I have no idea if there is treatment. I myself am considered MMI I wil never get better. I find that when I am in sevear pain (pain so bad I am crying uncontrollibly) the only thing I can do is go to the ER for pain meds. But for moderate pain ice or heat helps. Don't use heat on a new injury because it increases blood flow and causes more pain and swelling. Ice can be used at anytime. I was told to use ice 20 min on 30 min off. I also find that laying flat with my legs propped up on pillows, or on my side with pillows between my legs helps the pain too. It sounds like it's not very likely that you can see a doctor but you do need to because only an MD can tell you what the problem is and how to treat it without making it worse. I hope some of these tips help you out. Good Luck.