Have you ever tried yoga? It's great for toning muscles and helping with weight loss.
What are you doing now for exercise?
Weight training is a great way to loose weight and build muscle - use no higher than 5 lbs if you're just starting out and 15 repetitions with 3-5 sets of each exercise like bicep curls, tricep kickbacks, and push ups. For tummy try core strengthening exercises rather than straight sit ups.
Your own body is the best resistance for you right now! Try doing push ups before bed and when you wake up :-) good luck!