Matthew Stafford's wife, Kelly, is seriously regretting going under the knife to get a new set of boobs years ago ... saying her experience with the procedure was straight-up horrific.
Kelly detailed her journey on her "The Morning After" podcast this week ... saying she always wanted to have bigger knockers, so she saved up for years to make it happen.
"I just turned 19," Stafford said. "So I went and got a boob job."
Kelly -- who started dating the L.