What can I do!?!?!

I think you need to talk to a physical therapist about this.

I think Jen is right. A physical therapist would probably be your best bet.

I was thinking maybe stair climbs with weights? If you have stairs in your home, maybe you can pick up some dumbbells or use two milk/water jugs with a certain amount of water in them as dumbbells, and walk up and down the stairs at a pace that's comfortable to you? But you mention that stairs is sometimes painful, so that may not work.

swimming might be a good option

Absolutely, conferring w/ a PT but you said walking is something you can do, so by all means do it! Walking is cardio! Add some crunches, free weights for arms etc. Lunges and squats are great but they're not a defining be all/end all in terms of achieving fitness and cardiovascular health. Maybe there are things you can't do, but explore and identify the things you CAN do. There's a guy in my tri-training club who's a vet w/ a below the knee amp and femur rod w/ total knee arthroplasty and he's completed many marathons and tris. Don't give up, keep looking for ways to be active and incorporate fitness into your life and you will find so many rewards!

Does the bicycle motion hurt it? If not, you could try that. I picked up a functional exercise bike at Salvation Army this week for only $2 because I already had a bum knee and could only do walking, biking, occasional swimming and low-impact aerobics without hurting it. But now I have recently discovered I also have a hernia and my surgeon's consult is next week. In the meantime, my doctor said walking and biking are OK but not much else. (Swimming probably would be OK too but I don't have regular access to a pool for that) So my Fitness Blender (fitnessblender.com) workouts that I've been relying on during the cold and rainy Oregon winter/spring are kind of on hold for the time being. So the indoor bike is a Godsend to give me an inside option when the weather is not cooperating -- or I'm trying to kick a cold, like now!! I don't know if that would work in your case. But I've found that if I don't waste time bemoaning and making excuses for what I can't physically do and just concentrate on doing what I CAN do (which in the beginning was only walking and my knee PT), pretty soon I find I can do the things I couldn't before. So keep your spirits up and see your doctor or physical therapist like everyone is saying and just do what you can and that will slowly make you stronger to try things you never thought you could do....when it is medically advisable to try. But I would advise you to avoid any exercise alone just so you don't have a repeat of your getting stuck!! At least have someone nearby who can help you in case anything happens!! Be safe!