Legs falling asleep/numb after butt implants. Is something wrong?

This could be normal due to the pressure of the implant on the nerves and can worse after prolonged sitting. It should not be constant. Nevertheless, you should be examined by your surgeon.

You seem to experience a problem of nerve compression. This is possible, but somewhat unusual 2 months after the procedure.If the problem appears at this stage after surgery, an ultrasound or possibly an MRI scan to rule out a late fluid collection (a so-called seroma) may be a good first step.If no fluid collection can be seen, the problem is only in certain positions and tends to improve rather then aggravate, observant management may be most advisable. Most nerve irritations after this surgery are temporary. If you feel it aggravates you must liaise with your original surgeon. Depending on the position of the implants a short cycle of cortisone treatment might help if not you might have to remove the implants,

This is not an ideal situation. you must be evaluated by your surgeon to determine the cause and treatment.