I am 7 weeks post tummy tuck and BBL. I have skin necrosis which seems to be getting worse, the wound is getting deeper. (photo)

Hi
and welcome to our forum!
I
am sorry that you have experienced a complication of the abdominoplasty
procedure. During the procedure, the abdominal skin and soft tissues are
separated from the underlying musculature from the ribs to the pubic area. If
there is impairment of the blood supply to the abdominal skin, the segment of
the flap the greatest distance from its blood supply may not survive (above the
mid-pubis). The cause of the blood supply impairment can range from effects
of smoking, diabetes mellitus, vascular disease, previous surgery in the
area (disrupting the normal blood supply), infection, or may totally
inapparent.  
Treatment
consists of removal of the unhealthy tissue, followed by intensive wound care. You still have a moderate amount of unhealthy tissue as per your photograph. One looks for the development of granulation tissue, a beefy red vascular
tissue, to develop, after which time the wound will begin to shrink. Many
wounds of this size will seal over a span of 2-3 months. The depth of the defect is not the important factor as your deeper structures are intact. Some advocate the use of a suction
apparatus (wound vac) to accelerate the process of wound shrinkage. Various
enzymatic topical creams are available. Some advocate hyperbaric oxygen
treatments. In our practice we usually obtain excellent results simply with frequent wound management.
After
the wound seals, and after the scars mature and the inflammation
subsides, one would then consider revisional surgery if necessary (usually
6-12 months). 
Continue close followup and intensive wound care with your plastic surgeon.
Best
wishes...