I started skiing at 45. Between the ages of 48 and 51, I tore my left ACL, meniscus and mcl, 2 years later my right rotator cuff, and the next year my right ACL, lcl, and mcl. Three surgeries in four years. None of them easy to come back from full force when you the tender young age of old enough to be you dad. I coach kids each weekend. I race beer league and NASTAR and I ski about 60 days a season. Many of my ski days are training to be a better skier and includes bumps.
I still don't have an ACL on the left side because of complications during the surgery. I like to ski fast and I ski all day. I'm not limited by my previous injuries and in fact, because of them, I'm in better shape now than I was then.
Maybe you have to loose another season. So what? Your 19 and as I stated, except for a couple school trips in HS, I didn't start until I was 45 and I'm loving it.
One other thing I would like to point out, is a conversation I had with my surgeon about my ACL surgeries and which type to have. I was discussing the odds of it happening again, which type is stronger (cadaver, auto, hamstring etc) and things like that. He said there are all types of numbers being interpreted different ways, like young men were more likely to reinjure themselves where as older men were not. The arguments are whether it is because old men give up the sport that caused it or young men continue to do the sport aggressively and take chances. Or is it because old men recover slower, follow their pt more religiously and came back to the sport slower and young men don't give their body long enough to heal properly.
No one is really sure. I do think that what has helped me avoid re-injury (knock on wood) is that I constantly work at it; physically so I'm strong enough to not get re-injured due to fatigue, I work at ROM and flexibility so they aren't the cause, and I work even more on technique so I'm less likely to be in a situation I can't handle.
In the medical world, no one is surprised you re-injured yourself. They sort of expected it. I don't remember the exact percentage but it was something lbetween 30% to 50% of young men (under 34 I think) re-injure themselves (retear the ACL or tear the other ACL).
As far as weight gain due to inactivity. Sounds like you remained active with at least one activity - eating. Maybe cut back on that some.
You don't need to be completely inactive either. You have to be careful and follow instructions from the Surgeon and physical therapist, but your upper body wasn't injured and your other leg is still good. Don't look for things you can't do but what you can.