For over 1week i feel incredibly weak, i have no real symptoms,just weak and have a big loss of appetite. what could this be? i am exhausted always.

May need checkup: Tho 1 week is not long enough to define a condition as chronic, it's meaningful esp. if no signs yet of relief. My first suspicion: viral illness which can cause both short & long term fatigue syndromes. If symptoms persist beyond 2-3 weeks, need to consider other infections as well, anemia, endocrine problems (ie diabetes, thyroid) etc, etc, & so you'll need a thorough checkup. Hope that helps.