3 wks post op & center of TT scar is red w/yellow oozing. It doesn't look like there is an opening. What could it be? (Photos)

Thank you for sharing your question and photographs. I see your area of concern and it appears that you either have had a superficial separation of your incision due to tension or limited blood flow or some blister formation due to the steristrips and swelling that can accompany the procedure. As this is a change in your recovery I would reach out to your surgeon for advice on local wound care.  They can offer you the best advice but a nonstick dressing is an excellent treatment for now but would avoid hydrogen peroxide for now.  Hope this helps.

I see that you are paying close attention to your tummy tuck post op scar and surprising sometimes patients overlook this important aspect and end up in trouble or with a bigger problem. From you photos it appears that your incision is still covered by steri-strips and sometimes the ster- strips trap moisture and contribute to the softening and increase redness of the scar. Remove the ster- strip and allow the area to be exposed to air so that this area dries and begins to heal.. If the area gets increasingly red call your physician  to report a possible infection which is called cellulitis. BTW, your garment which creases and folds in this area can also contribute to tummy tuck scar irritation and break down. Try to keep this area free of garment compression. One to two more weeks of scar observation will be needed and then you should be beach ready.. Success to You!!

It looks like you either had some separation or loss of skin at the incision closure. It looks very superficial and more than likely will heal with local wound care only.  Best to be seen in person to be sure.