5 days post-op. Is it possible to tell from my pictures if this is a hematoma? Do I have a reason to worry? (photos)

It would be better to see your surgeon in person so that they may assess it, rather than sending photos.

There is no way to tell for certain from a photo, but your pictures are very concerning for fluid accumulation below the skin.  This may be blood (hematoma) or a serum (serous fluid).  In any case, though, you need to contact your surgeon as soon as possible to be seen and evaluated.  This can be drained in the clinic, but if left in place can lead to pain, infection, and even scarring that can alter your outcome.  Please contact your surgeon.