This is hard to address in this forum. Based on you description, this surely could be seroma but only person that can address this is your plastic surgeon. Please have them reevaluate this issue for you. Good luck. Hope this helps.
There aren't really definitive questions you should ask, because so much of the answer depends upon how things look on the physical exam. If indeed it is a sinus track down to a seroma, the wound may need to be probed and scraped the bit with a curet. Visit with your plastic surgeon as a starting point, and he or she should know what to do from there.
Best of luck!
Board-Certified Plastic Surgeon
Newtown Square/Philadelphia, PA
It sounds like you may still have fluid inside, and at 12 weeks to still drain is concerning. DO you have mesh from your hernia repair? Could this be infected? Best to be evaluated in person.
This could be a liquified hematoma or a seroma. Either way it needs to be addressed by the plastic surgeon.