What can I do as an ADC when behind and being camped?

Hey guys, looking for some insights from better players (which are not hard to find, as I'm a s5 scrub).

Last game I've had some real troubles trying to feel useful to my team. Let me put a small background with the biggest points, so you can see what happened:

• Had a decent lv 1 and 2 in my Draven (me) & Sona vs Varus and Lulu
• At lv 2 Sona ate a lot of poke
• At lv 3 or 4, Sona overextended a bit too much and I stepped in to try to save her. I became the focus and died. Saved the Sona, but burned my Flash
• Got behind in gold and they started to poke us out of lane
• Got killed once more in a 2v2 after an Amumu gank left us at 50% hp
• Got a kill on their Lulu
• Our Mid Raka tried to gank, but got counter ganked by Amumu and died with Sona
• Lee tower dove the Lulu with me, but he walked away from tower range and I got killed by it. She survived due to her ult

After this point I became completely useless for the team, not being able to walk into lane against anyone on the enemy team without having to give up a lot of CS or risk dying. Meanwhile, the enemy bot lane was able to pressure other lanes pretty hard. I tried my best to farm it up and hope to reach late game, using my Ult to stop pushes or to put some AoE damage on fights that were happening far away instead of trying to snipe kills (specially because it was very rare for anyone on the enemy team to get really low).

During this awful early-mid game, I think I've been ganked by Amumu about 3 or 4 times, and got no ganks from Lee Sin. Well, he showed up to clean up a few times. Lee also taxed me hard two or three times, which made coming back really really difficult for me.

So, what can I do as an ADC to get back in the game after falling so far behind? Is it worth it to be more selfish and leave my allies to die? Because I think about 50% of my deaths happened when I tried to help someone escape or win a bad fight.