Lower back hurting for 4 weeks.getting slowly better; but still no lifting left leg to the front or bending down+coming up.weak+tight or need mri?

Depends: If you are getting a lot better, you could probably hold off on the MRI. Even if you have a disc herniation, they can heal over time. So in an improving patient, there is very little you would see on an MRI that would change management options.

If it's getting : If it's getting better - not sure an MRI is indicated. Typically these types of problems resolve within 2-3 months. I know, it's annoying and frustrating that it takes so long ... But stick with it. Perhaps some physical therapy might be helpful to speed your recovery. Hope this helps!