Tuscan

Hi guys, I am currently learning French and German and I am struggling with one major problem... it makes me super tired. It wipes me out and I actually have to stop and either do something totally different, or sometimes actually even sleep. As a result I am not getting very far because I can't spend that much time studying. I can read a book in English for hours, cover to cover no problems.... but I am reading a book in German at the moment and after a few pages I am zonked, and fall asleep (it's not a boring book). Does anyone else suffer with this issue? Any ideas how to get less tired and achieve more? It makes me feel super lazy and un-dedicated. Thanks