Why am I being put in GM/TOP 500 lobbies?

okay so basically I ended diamond 1 last season on dps then this new season I went 7-4 which got from plat 4 to plat 2 then I went 7-0 and went straight to diamond 3 and then 7-0 again and now im masters 5 but its putting me in lobbies with people who were gm and even in the top 100 and I just lose as they are better then me.