Do you have any reason not to trust the mechanic you are presently using? I agree that the trans flush was probably not a good idea - I would have done a drain & refill only - don't use the shop that sells the trans flushes. Is the timing belt broken?
At this point, the car would be a very tough sell, so your options are fairly limited. The best time to sell a car is when it is running flawlessly - try to put yourself in the shoes of a buyer.
I take it that you did not have this Camry examined by a mechanic when you bought it because people told you that Toyotas were indestructible and the ultimate in reliability and now you are disappointed. The Camry was a good car when new, but wears out no differently than any other make & model out there. This one is 14 years old and any car that age requires lots of attention to preventative maintenance to keep going strong.