Could you provide a specific list of what these diet professionals told you to do? I'd like to see first hand what they requested of you.

Assuming they gave an appropriate diet, and you actually did follow it precisely, I suppose the next best thing for you to try is add in exercise into your daily schedule.

Exactly how many pounds did you gain so suddenly? Over how long of a time? If you had a fast metabolism, I can't think of many reasons why you'd suddenly gain "lots of weight" in what seems to be a short period of time.