I got in a car accident a month ago, and get tired easily because of it...now I'm out of shape. Exercise help?

At the end of June, I was in a car crash. I've been getting a lot better since, but, I find that I still get tired very easily doing physical activity. It's been getting better, but, as a result of my lessened physical activity, I have been getting noticeably out of shape. As expected, I no longer have the muscle definition and strength I had before.

I'd like to do some things, but working out still causes some pain. I can do curls and some such weightlifting alright, but I cannot do things like situps and pushups, and have trouble with a few stretches.
I used to have pretty defined abs, now I look to have a small gut. I have a healthy diet and watch what and how much I eat, as well, so, it shouldn't be much of a factor.

About 2 years ago, I lost a lot of weight, so, maintaining my physical fitness has been important to me. Situps and such were a big part of that because I could do them home in my room at any time, without going to a gym to use their weights. I have some freeweights at home, as well.

Anyhow, my goal for the summer was to gain 10 pounds of muscle, but due to my accident I have since lost 8 pounds, probably of...well, muscle.

I'd like to do what I can in the remaining 5 weeks of summer, but, at this rate, besides doing what little lifting I can at the gym, I don't know how.
So, it's not a big deal, I can put up with just not going to the gym and such, but, my new summer goal is to at least get somewhat toned again, and hopefully that may speed up my recovery as well (I have basically no endurance running and riding a bike - a 30 minute bike ride will have me tired for hours, now).
What're some practical replacement exercises for situps and pushups that I can do at home, without equipment?

Weightlifting is not the best thing if you are recovering from an accident... try to focus on cardio work like walking the threadmill and other cardio exercises. Keep eating healthy food also.

talk to a personal trainer and your doctor. a good way to start is going for short walks outside. everyday, make the walks longer and longer.

Tai-chi and Chi-gong would be good for you it's a constant movement with out straining your self ,it's a whole body movement.
visit real age work out to get info.

get 10 hours of sleep with a lot of fruit

Try pilates yoga. Not too much contortion stuff but lots of stretching and toning. Concentrates on breathing and doing each move with maximum effect. This can be done at home in front of the tv on the carpet. I have one that Kathy Smith the model does for abs and it's a killer. Also the one for total body is good. Do what you can of it and don't do it all if it hurts. You'll find you can do more and more as you learn to do the easier stuff correctly.
Go ahead and continue your biking but don't do as much and exhaust yourself. Do some walking and a few stairs but give your body time to recover. Variety and not doing damage to yourself is the key.
Good luck!