I honestly can't tell too much that you have a underbite but, I do notice your nose tip and the nasolabial angle to be acute.
I had the same issue and I wasn't keen on getting the Lefort 1 and thought I could live with my bite as is and went with the option of a premaxillary implant and a nose job. It did wonders for me and completely masked the exterior but, my smile was was off and now I'm considering getting the Lefort 1 to fix my bite and my retruded nasal base and maxilla (masking it didn't solve the underlying issue, though the exterior looks very good). The face and structure is always changing so, you have the option to mask it (like I did) or go the invasive route to possibly fix it and come out looking better *crosses fingers*.
The headgear you most likely had to wear was to pull the upper jaw/maxilla forward but, the problem with it is that without proper oral posture and continuing the use of the headgear, it will go back. Oddly enough, breathing through your mouth, having poor posture and limited chewing causes the maxilla to tilt downwards over time. I've been treating myself with proper tongue posture and tried to do more chewing and it's already done a pretty good job of pulling my maxilla forward and helped my bite too; keep in mind I've been doing this for a year.
Best of luck to you.