Hi Sebrina,
I want to congratulate you on your dedication to exercise and your tremendous weight loss so far. You have accomplished so much already! I don't want you to be so hard on yourself. First of all, losing three pounds in a matter of days is not necessarily healthy. Try to remember that this is in fact a life-long journey and if it take an extra couple of weeks to get to your target weight, that's OK. Just like quitting smoking, you can only control one day at a time, and if you get too far ahead of yourself, it can be daunting.
You are doing a fabulous job with your workouts. It sounds like you are ready to challenge yourself soon with a longer aerobic video and your walks (incorporating hills and speed) are great. Eventually, you will be able to jog comfortably, but that should be a goal in itself.
I wouldn't try to do MORE right now, especially since you are sore and you seem to know your limits. The combination of cardio exercise and strength training will continue to be key to burning calories and fat while you build lean muscle mass, which will help perpetuate more fat burn. Make sure when you are lifting, you are giving your muscles the appropriate rest to recover and rebuild. You should never be lifting for the same muscles on consecutive days.
Keep doing what you're doing. If you want to change something, try incorporating new exercises into your routine to mix things up and further challenge your body. Cycling, dancing, swimming, elliptical, whatever it is. Also focus on your intensity levels. Intervals are really effective for burning calories and fat and they're easy to incorporate into your walks.
Please be proud of your progress. I know I am. Keep me posted.
Good Luck,
Paul