Try aerobic exercise e.g. jogging, power walk, cycling or swimming. Aerobic exercise is the best way to burn off fats in your body.

Your muscles are still there, just need to be toned again. But they are covered by fats now. So burn the fats first before toning them again.

By the way, good body shape you had there. Don't give up!

then why some body builder have months of "off" period?

no, not off season, is completely off from the gym.

I forget If I read this regarding strength training or for bodybuilding.