How long should I wait to use elliptical trainer after knee arthroscopic surgery!

I'm at 5 weeks post surgery...still in quite a bit of pain, feel very vulnerable. Now I have bone on bone, where I didn't before.

This is gross but I can feel and hear it grinding and cracking even in the pool! Does it all the time now since surgery, but am hoping it is just a matter of healing and time.

Have a lot of weight to lose and I need more physical activity than swimming, even though swimming feels like just gentle therapy, not for weight loss in any way.

Can I push myself or wait more? (they said count on 6 weeks of healing, whatever that means). Surgeon said I need a whole knee replacement for sure, but I'm too young (49) and won't do it until I am 65. Plus I have to be perfect weight, which I am working on and understand.

Thanks!!