My skin feels like it's too tight every time I get up from lying down or when I sit too long. What could be going on?

Hello dear!!
Thanks for the question and provided information as well.
The sensation you are experiencing is due to swelling. You are still early on the healing process, it can take up to six months to see your final results, so please be patient. At the stage you are in, inflammation is normal.
If you have any concerns, please follow up close with your plastic surgeon.
Good luck :)

Hi and welcome
to our forum!
Congratulations
on your recent procedure...The procedure of liposuction is an
"insult" to the soft tissues, resulting in swelling which will
initially totally obscure the operative result.  The
purpose of a compression garment is to prevent bleeding and to control
swelling. We usually recommend its use for the first 4-6 weeks after the
procedure. 60-80%
of the swelling should subside within the first 6 weeks, with the remainder
slowly subsiding over 6-12 months.
It is most likely residual swelling causing the tightness, but if concerned you should visit your plastic surgeon.
Best wishes...