Pain in low back and left butt down in back of leg. I received butt implants intramuscular about 4 years ago.

 Again, an in-person consultation with physical exam is necessary before accurately giving advice on this question. That being said, if you’ve had pain ever since the surgery, it may well may be the position of the implant is compressing important structures - either bone and/or nerve. To remedy this, either the implant will have to be temporarily removed for about six months before it can be replaced into a new pocket or completely removed and never replaced. This depends upon your desire to keep the implants long-term.

At this stage of your recovery, you should not have any pain or discomfort.  You should go to your surgeon for a complete in person evaluation.  The right surgeon will listen to your concerns and go over your options.  Be sure to choose a Board Certified Plastic Surgeon who specializes in this procedure and is well known in the community for it.