Excuse the typos/grammatical errors if I missed them.
Since running isn't an option, perhaps for cardio you should try jump roping? If you don't have any, it isn't too difficult to find a substitute lying around. You only need to do it one or two minutes at a time. If you get tired quickly, that's pretty normal. You want to keep in mind you don't need to jump high, the rope is only about a few mm thick. You don't want to exert more energy than you need to. The most important thing is to get your heart rate up and the blood flowing.
As for weight-lifting, it's pretty hard to do that without any equipment. In this case, it's better to use your body weight as resistance than not doing anything at all. Pushups and dips are best. Make sure you have good posture, otherwise you could possibly hurt your neck/back. Do these long enough, and you should start to feel some definition in your deltoids.
You also want to do stretches, especially straddles after warming up. Try doing a split (it doesn't matter if you can't go that far), sit back, and stretch from side to side. Not only does it prevent injury, but it feels pretty good too.
Something I have to stress, don't forget to breathe. Your breath might get shallow while you're exercising, so it might cause you to get dizzy and light-headed. It doesn't help if some of us are suffering from a poor diet, heck, I'm pretty anemic myself.
Sorry for the wall of text. It's not nearly as stressful as it seems. It can actually be fun, especially when you notice your energy level begins to increase. Good luck!