TH8 is one of the worst TH's to get pummeled because the TH9's with lvl 6 troops farm on TH8's A LOT and there's not much you can do about it.
As far as constantly getting attacked by higher trophy folks it's just a matter of chance and matchups. When you next through your bases, do you attack the harder TH9 with more trophy's than you or the easy TH7 with fewer? It's the same for the TH9 that's attacking you, so you will more times than not get hit by somebody stronger than you and it's just part of the game.