I had septic arthritis three years ago and had a thr three months ago. Last weekend I was body slammed onto my replaced hip. I can now barely walk?

Get X-ray ASAP. See your surgeon asap and get an x-ray to rule out a fracture or dislocation of replaced joint. Get on crutches until then. Ice to hip. Modify your activities so the replaced hip will last as long as possible. Given your young age you might need revision surgery in 15-20 years if you continue high impact activity and 25-30 years if you are careful and stick to low impact aerobic exercise.