I've been doing cardio and weights to lose weight it's been a week i'm in muscle pain is that a good sign that it's working and i'm burning fat?

No.: You are experiencing delayed soreness of exercise. If you have pain during your activity-cut back. This means overdoing it!

Maybe not yet: First of all, congratulations on your new exercise routine! what you are experiencing is delayed onset muscle soreness (doms). This happens to virtually everyone when starting a new program of strength training, and is worst 48-72 hours after initiation. In general i advise people to ease into strength training and gradually build up the intensity over the first month.