What is this lump after my tummy tuck?

You appear to have a seroma after your tummy tuck.  A seroma is a collection of straw-colored fluid under the skin--the fluid is what your body normally produces as part of the wound-healing process.  Sometimes more is produced in a certain area that the body can absorb, so it makes a "puddle".  Typically, this happens when the drains are removed soon after surgery, when compression isn't used faithfully, when a woman returns to increased physical activity too quickly, or in heavier women (fatty tissues make more of this fluid).  Sometimes it happens even when none of these things applies--it can just happen.

I'm thinking this isn't a hematoma because there's no pain and no increased bruising of the skin over it, but it still could be a hematoma nonetheless.

I doubt it's a hernia because you can only see it when you're lying down.

A seroma is treated with serial aspiration (using a needle) or by drain placement.  Please do get back to your surgeon for evaluation and treatment.

Regarding: "This picture is taken while laying down first thing in the morning with bladder FULL to show it at largest- No pain from it ever. It does shift from below belly button on right- some days directly below belly button and crazy enough one day on left! Mornings laying down are key time. I can not feel it standing up. Once in awhile I feel it at night. My plastic surgeon blew it off since he couldnt feel it standing up so after seeing picture said "wow- you need to have that seen" What do I do?"

I have done several hundred Tummy Tucks and have not seen something quite like this before (time line, description, symptoms).

It does NOT sound like a hernia (? reason why your surgeon "blew it off"). Hernias are WORSE when standing and straining. Do not sift sideways and get more painful when upright and usually get less painful and may even go away when lying down.

Tumors VERY rarely develop so rapidly and are usually fixed and do not shift.

It most likely is a seroma, a fluid collection.

I would recommend you get either an Ultrasound or CT scan and have it looked at. If it is fluid, your doctor should ask the radiologist to put a needle in it and draw out the fluid at the same time.

Good Luck.

Dr. Peter Aldea