I had plastic surgery on sept 11. I now have a hard lump extending the length and width of the incision. I had heavy Lipo in my back and abdomen too.

Lumps after Lipo. lumps after Lipo csn be pretty common. They will soften up to 3-6 months. If there longer they may be permanent. Some can be improved with tissue break up techniques.
Could be normal. Could be normal healing process with local inflammation, scar tissue formation and possibly hematoma formation. Make sure it is not red, oozing pus or very painful. Fever? If any of these, I rec seeing a dr.
Go see your surgeon. Can be a skin 'reaction' like a keloid, some blood collection under the skin, or an infection/abscess/something else. Go and see your surgeon. as soon as possible.