>because I can't fight and can't farm
I don't want to sound like a broken record, but many of your problems with carries can be fixed by learning how to farm better. It takes time, but once you get the hang of being a master ricer, everything else will fall into place.
As a position 1 safelane carry with a support or a solo mid, aim for at least 50 last hits by the 10 minute mark. It's hard to do, yes, bit it's possible. If you have a problem with timing last hits, change your choice of starting items to get better stats or a quelling blade. If you're on the safelane and your lane is pushed out, you can move to the jungle and clear a camp while you wait for your lane to fall back. Every second in matches matter, so use your time accordingly and make every action count.
One thing about AM is that he's more situational than most other carries. Pick him when playing against at least one hero with a high mana pool that is always empty. Examples are Storm Spirit, Skywrath Mage, Pugna, (a good) Invoker, and Lina. Because, well, he counters mages. Of course, the extra magic resistance is only useful when playing against heroes who deal a lot of magical damage. AM also needs plenty of time and space to farm, so heroes who can make space and/or prolong the game are valuable teammates. Treant Protector, Tinker, Techies, and Nature's Prophet come to mind.
If AM seems like a good choice, when at the hero selection screen, hover over AM and ask if anyone is willing to support
you. If you don't have anyone to support you and you can't take the mid lane, pick a different hero.
I used to play AM the way I imagine that you do and my winrate suffered because of it. I thought AM was an overrated hero, since everyone called him a hard carry but I could never make him scale well enough. Then I riced hard, I bought better items, and I tore people new assholes.
Farm when you can, wherever you can, and avoid fights until you're AT LEAST level 16 with some good items. If your teammates suck, you'll need to reach these goals earlier, which is why farming well is important.
Some of my favorite items to build on AM are Battlefury, Butterfly, Abyssal Blade, Manta Style, Assault Cuirass, and goddamn Daedalus. Seriously, Daedalus is such a game-changer late game and I think it helps Andy Mage pay off so well, especially with Battlefury and Manta. Don't be afraid to buy it. Since you're having trouble with surviving, build items that will give you survivability while also increasing your DPS, like Butterfly, AC, and Skadi.