Lifetime and 4 weeks stats are wrong

I don't know if this is a problem that other are having, but my lifetime and 4 weeks spotistats are surely wrong.
The 4 weeks show only four artist, and i mean i didn't listen too mutch music in this period but it's simply wrong. The only the only possibility I can think of is the fact that i'm not listening a lot to single artist, so i don't make enough stream for a single artist, but i don't know.
The major problem are the lifetime streams, i think it lost part of the old streams because artists I've listened a lot in the past have disappeared for artists I've listened recently, but much less. In particular my actual second position is an artist that i've surely listened less than almost other 20 artists