Spots on my Phalaenopsis leaves :(

[onlymemyselfandi]

Hello, i bought this orchid few weeks ago and i noticed some spots on its leaves. At first i didnt pay too much attention thinking its not something important but now those spots increased and the lower leaves began turning yellow. Those spots from the under side of the leaves have something like white core? Also i noticed there's some brown things like small insects on it..maybe its that causing it? Besides its leaves though it seems to be good, its on blooming right now as you can see on the pictures. Can you please tell me what shall i do? Here are some pictures of it:











Oh and by the way.. i'm from Greece (so you can imagine the climate here).. how often do you think i should water it? And general what care should i provide to it? I have it inside the house, in front of a window because its winter here and outside temperature is low. Thanks a lot in advance for your answers!