Am I trying too hard with my body?

Recently, I've been losing boat loads of weight. I'm an average 16 year old boy, I weigh just under 9 and a half stone. I lost the weight and realised that I was now just a skiny little bastard with no muscle at all. My dad suggested I used this thing he had called a 'powerbow' if any of you have heard of one before? I can't really explain it so google it if you're unsure, and i did start using it, just 10 pushes a day, and 10 pulls each arm a day for about a week & a half, and started to notice a difference. I could never normally bemd those huge springs with the handles either end, but now i can with ease. I've started bending the spring (excuse my maybe wrong terminology) aswell as 10 curls on each arm with a 20kg dumbell, in addition to what i previusly explained. Its no strain on me, it just sounds like a lot to me. Thanks :)