You need to work on a few things or these games will keep happening periodically. One of them being is your build order. Way I look at it is some games you will get it won't matter what you build as long as you have your core. This is because the threat from the enemy is not so high you don't need to worry about it as much. In this case you do. What I would do is just before the game even starts just think about what you will build. You need 2nd zeal item. Caitlyn just doesn't feel right without the 2nd attack speed item. So this is what I would of done. BF -> Zeal -> Complete Hurricane/RFC -> Complete I.E -> Third item Hurricane/RFC -> Mercuiral -> ARMORPEN/BT if YOU think you need steraks if you believe your positioning isn't good enough. This build you great damage and survivability with the qss for amumu and irelia. You just need to stay alive vs zed which is not that hard if you just position correctly and have flash/heal any maybe some peel lol. I would also like to add that you need to work on your cs'ing in lane and looking to abuse your opponents weak laning phase. So basically the way that lane works is they want to poke u and sustain if u just take a trade. The way you win that lane is taking SAFE trades by poking with q and auto. Also you rely on the thresh to land hook so try to make some space. Also try abusing the level 2 power spike if your support is down.

Some takeaways: If you want to get better focus on your weaknesses and work on them. (Also you need to play A LOT more.) Work on fundamentals 1. Cs'ing 2. Trading 3. Map Awarnesses 4. Cookie Cutter Builds 5. Objectives 6. Positioning/Spacing

Hope I could help :)