If you have never seen a liposuction on T.V. or on the web, its not a gentle process. Also, the more tissue that had to be removed, the more likely you are to feel more pain. Surgeons are different, some being very gentle with tissue handling and others are rougher. If you have drains in, sometimes they can cause some discomfort when you move.
If you are living with someone, they can help you sit up. One thing my surgeon had me do during the day after recheck, was to push against his hand which was on my back as I lay down. It made a huge difference and its something another person could do for you. My surgeon also reminded me to take deep breaths a few times every hour to avoid problems from shallow breathing.
As always, if you feel that the pain is greater than what you would consider normal, call your Dr. Its always better to call and find out its not a problem than to wait, try to work through it and find out that you really do have a problem.
sam1234