well lets see..the bad news is (as you have stated) you are bad, the good news is you can only get better now. last hitting and map awareness (wards) is 90% of the game..to get better at it, i suggest a number of things..
first..watch some streams of other people playing. myself i prefer going to lolking.net and watching zekent as he is very calm. thats just 1 of many though and i recommend viewing a lot of different people regularly.
second.. PRACTICE!!! cant say that one loud enough. cant improve without trying to get better
third.. stop berating yourself, it just doesn't help. there are enough toxic ppl that will do it for you anyway.
fourth..don't allow yourself to become a toxic player (those are the ones that actually "suck" )
fifth..keep an eye open for friendly ppl willing to help and ask for assistance. do not be afraid to tell people you are new or that you need help getting better, the good players will jump at the chance to help you.
and lastly..you may add me in-game if you need someone to play with that isn't a rager or a giant D-bag. im not real great myself either, but that doesn't mean i can't help others be better than i am^^ squeek