Lost a game I should have won so bad earlier today

I was playing Anivia middle lane mage against a Zed assassin mid lane.

I shut him down early going 4-0 and he began to roam, I warned bot lane that he was coming and for them to back (I didn't rotate with Zed because I had 0 mana and needed to back)

He gets a double kill...

That's cool, I am still ahead. I then get turret as I get back in lane.

Fast foward 20 minutes.

We're all ahead except for our ADC Miss Fortune.

That's cool, I'm carrying and our top lane Yasuo finally got ahead and started doing a little bit of carry.

Shyvana is toxic as all hell but she is at least trying to secure objectives and pushing lanes when needed.

Suddenly we are so ahead that we could end in 1 final push.

....

Adc and jungle begin arguing with support and top lane. I'm over here trying to push and I get 1v5'd. I kill 1 but I get my first death.

Fast forward some more, we start losing team fights and the enemies catch up and wham

We lose.

GGWFP

I ended with 20+ kills and 3 or 4 (don't remember) deaths.