How long will my lower back pain last? I strained it lifting weights a few weeks ago. And it still hurts. Thanks in advance.

LBP. Usually most resolve with conservative treatment within 4-6 weeks . if persists consider MRI, Conservative treatmetn includes a few days of rest no lifting, NSAIDS, muscle relaxants sometimes steroids, ice/ heat compresses, lidoderm patch, gabapentin sometimes, PT( laser can be very helpful), I use kinesiotape. f/u with doc.
Hold the weights. See your pcp for questions re lower back pain, possible muscle sprain and guidance on cardio. Hold off on weights until no more pain. Consult with a trainer to avoid injuries, work on strengthening core muscles. Walking, swimming, stretching also good. Great you're exercising.