Just had a pretty ****ed frustrating game against a teemo bottom. I couldn't do anything at all because between his blind and poison he won every trade by a huge margin. I couldn't just sit at my tower farming because I was falling behind in CS hard. Seemed like he pretty much auto won the lane. Is there anything I could have done, or is Teemo pretty much just an autowin in bottom lane?

Teemo is far from auto-win.

First of all, who were you playing as? Teemo's range is average, and there are plenty of AD ranged champs that can out-poke him.

Secondly, who was your support? Know how to sync up with your support's skills. I think a long-ranged champ paired with a sustain champ, like Soraka or Sona, should totally be able to stomp Teemo just fine.

Cant help you if we dont know who you were playing.

I was playing as Tristana with Janna support. He had nunu support with permanent blood boil. I know that after a few lvls I'd outrange him, but with his movement speed I couldn't actually poke without taking hits myself.

To stop an AD teemo you basically just need to counter the CC. Teemo is incredibly squishy in most cases. A stun, silence etc... should be plenty to win the trade. Even if you call someone from mid or top to come gank and gang up on one teemo to shut him down for a minute so you can get your CS up and potentially damage or destroy the turret so you can begin to roam. (He can't stop 3 in most cases without shrooms, anyway)
If you're not going to commit after the blind, run away as soon as you're blinded so you don't lose valuable HP from waiting to be able to deal damage again. Also, if you initiate, don't use all of your abilities first off as when you are blinded you can still use abilities. This will stop you from losing the few crucial seconds of dealing damage and keep applying the damage towards the teemo at a consistant rate.

dive bomb dat hoe

With it being a situational strategy game, you shouldn't always go for cookie cutter builds. Buy items to counter his strengths and play on his weaknesses. Janna's shield and tornado should have helped a bit, if they were being a timely supporter.

Don't stand there and fight after be blinds you.

I think the answer is "Why so bad?"
I main Teemo and he's very easy to counter, for starters he wont have any heals so harrass him even if its just Janna's Tornadoes, until he's roughly half health. Janna shield, Rocket Jump, Ult into tower, WIN.

In this case, the best way is to level up your e first to help you farming. You should be out farm teemo very easy.

Also, use regrowth pendant as your start item. With Janna's heal and the pendant, you shouldn't have to worry teemo trading