Dear Kissimmee:
If you have questions about your specific surgery, you should call your plastic surgeon. Asking in this kind of forum is great for general information, but specific advice requires specific information. Swelling is common after a tummy tuck, and will take months to resolve. If the massage is hurting, you may want to wait until it doesn't hurt, and you should contact your plastic surgeon to be certain that there is not a problem. That is part of our job, so your plastic surgeon should be willing and able to provide you assistance if there is a problem, and peace of mind if everything is ok.
Fluid collections, usually serum, are not unusual under the skin at three weeks after a tummy tuck. This is why drains are left in place after the surgery. Serum is the liquid part of the blood. Serum is clear, like the fluid found in a blister, but can be blood tinged after surgery. These types of fluid collections are normally found in the lower abdomen, not in the upper part. If small they can be ignored. If large and uncomfortable they can be drained. Frequently they recur until the abdomen has healed sufficiently.
Whole blood under the skin is not common at three weeks. This is a sign of frank bleeding, and may require additional care. It usually presents as increasing pain and a fluid collection under the skin, and is most common within a few days of surgery. Since skin is opaque, the only blood you can see, is seen as a bruise.
With any plastic surgery procedure, if you have specific questions about your surgery, or how to take care of yourself, your board certified plastic surgeon is your best resource. They know you. They know the surgery, and they are best informed to take care of you.