Failed ACL Repair, gives out...what next?

I have something similar going on. And I just found this site.
Last year I had ACL reconstruction and Minscus repair. I went to rehab for a while and was doing great exercising at home. Than things got busy at work and I slacked off on the rehab (I would also work 2 full weeks before getting a day off, not that my job is heavy labor but it's a lot of standing).
Than about a month ago I started feeling some pain and minor popping. A few days later I stepped down from a curb and the knee gave out and I was in hell for the next few days.
A few nights ago my knee gave out again.

I first tore/ripped the knee when I was 22 and the surgery when I was 24. And I'm in the process of contacting my last therapist/trainer.

Hi. This forum was helpful for me when I originally tore my left ACL some 5 years ago (full tear, 75% meniscal tear, bone chips...)

I was skiing this past Jan and fell, felt that "pop," knew something happened. Not lots of pain, but some swelling, limited range of motion, and instability. Went to my Ortho Surgeon who said the original graft (allograph) had not vascularized, and that rehab had tightened up the muscles around the ACL, which is why I hadn't had problems.

She suggested phys therapy, no surgery. I went through a course of phys therapy, got full ROM, and went on my merry way. She did give me a brace and suggested I wear it for torsional sports.

Well, I didn't follow through on the wearing the brace part, and found myself playing wiffle ball (yes, wiffle ball!), where a close play and a slide caused that same "giving out" sensation. Now, two days later, it's swollen, a little sore, and feels unstable and ROM limited...I know some of that's the swelling.

I called my surgeon, she'll call back I'm sure, but I'm wondering if any of you ACL vets out there have any advice...am I going to have to contend with this for the rest of my life? Would the brace have prevented this? Should I consider surgery? Is it possible I've done other damage to my knee--cartilage, for example--and ought I to push for another MRI?

It's all depressing. I should add that I've also had an ACL repair on my right knee (hamstring repair) and that's held up just fine, no issues...but I don't want to go through the surgery again unless I have to. OTOH, if I'm always afraid that it's going to give out, that's no good, either.

BTW, I'm 51.

Thanks everyone!