Body & Muscle Building

bodybuilding increase weight
Wight lost around my waist so fast, please help!?

Hello, iam at 19.5 years of age I do not know the exact height and weight, but it is in the ring 175cm [5.7 feet] tall something, and weight 70 kg .. as I do bodybuilding and some freestyle, now the problem is that I lose around my waist Wight very, very fast, I mean within 1 month I lost enough weight to not carry as 70% of my paintings, lol! (note: when I lose that weight does not become weaker, I became stronger with more power and can increase the weight on the practices of bodybuilding too) are now losing as much weight as this in just one month of the period just made so worried!, so this is normal for my age and lifestyle practices? Do you think that cauze lose weight athletic practices or cauze something else like not eating enough or not getting enough sleep?