Is there anything I could go to fix the "lines" that are now there and sagging skin? (photos)

Because of the sizable amount of connective tissue the area that was treated is prone to contour issues. Short of retreatment I'm not really certain there's much of a solution to the problem. Whether or not retreatment would be a possibility requires physical examination.

 Liposuction is great for contouring, however it can leave irregularities in the skin. This is especially likely when fat is removed from the area right underneath the buttock. Unfortunately there is nothing guaranteed to work to improve this, but Ultherapy or other tissue tightening treatments may improve the look. They work by tightening the connective tissue fibers under the skin, which can lift and tighten the tissue. The effect takes 3-6 months to see after the treatment and can last more than 2 years. 

Thank you for your question. Unfortunately, cellulite is a
condition that can affect anyone disregarding their weight. Diet, exercise and
endless creams will not improve the appearance of cellulite, but there are
promising procedures to eradicate the severity of dimpled skin. The Cellfina
system presents a long-term, one-time procedure to eliminate the appearance of
dimpled areas with Cellfina. This innovative technology involves a subcision of
the area, performed totally under local anesthesia. Cellfina™ eliminates
cellulite by inserting a microcannula which has a blunt tip (like a Q tip) to release
the connective fibers of the skin. The underlying fibers are released by
detaching the fibers that pull down on the skin, which results in dimpled and
lumpy skin. As a result, the skin will smooth over in just a couple of days
with one treatment, reducing the severity of dimpled skin. The final result is
a smooth and healthy look. Minor bruising and swelling may occur. The recovery
process varies from patient to patient but the majority of individuals are able
to return to normal activities the same day. Remarked improvement in the
appearance of cellulite can often be seen within three days post-treatment.
This procedure has long lasting results that last at least two years for most
patients.

One of the procedures that may help is a repeat liposuction with extensive pre-tunneling to separate the fat.  This could be combines with lipo grafting in hollow areas.  Some of the skin tightening procedures like Thermi-RF or Ultherapy may also help.

YES! There are 3 options: #1 Non Surgical -  the new Thermi 250 RF in at least 6 to 10 sessions at $400/session can offer results. Or Resolution MD cream system @ $160. #2 Minimal Surgical - Cellulaze with the Dr Bs modification of pre pickle fork release (acts like CellFina but better). Fee $4,000 #3 Or combination of #1 & #2

There is limited information from the photos you provided, so I recommend a full exam by a board certified plastic surgeon.  Depending on your findings, you may need a revision or replacement of some of the lost volume with fat.  You may have options but it is hard to tell without an exam.