If you over do exercise…you can actually wear out your muscles and end up with a bigger problem.
45 minute cardio with 30 minutes of weights or strength training is fine…no need for anymore than that.
Please please please do not skip breakfast…since you have been skipping it your body is used to being deprived. Get into the habit of having breakfast again…this can be the biggest meal of the day for you. Have lunch and also dinner but no later than 7pm.
Overdoing anything: working out, eating, not eating, vitamins, etc etc etc…can hurt your body. Everything in moderation.