I'm going to write this out as I watch the video.
1. Build your supply depot at 10 supply. You're behind economically and you've only just started the game. It also puts you behind for producing units and tech in the future. You can't make a barracks until the depot is done.
2. 2 depots before barracks is bad. You should be making a barracks on 12 supply, and you should immediately make your Command Center into an Orbital Command at 15 supply. Anything else is bad.
3. The only reason your Barracks came out on 12 supply this game is because you aren't producing SCVs non-stop. That is bad early game unless your build specifically calls for you to not build SCVs, and those builds are advanced.
4. Why the Engineering Bay early? You aren't even using it.
5. At 3:17, he has 17 workers to your 13. You are practically irreversibly behind at this point, and neither of you have even made a combat unit yet.
6. You didn't put workers in your first gas geyser, but you built a second one and then put workers in it instead.
7. You're making an absurd amount of Supply Depots early on. That money could have been used to make an expansion or more barracks.
8. Idle workers way too often.
9. Didn't get guys in your initial gas until 8:00.
10. You made a Tech Lab on your Factory but you aren't using it (so why get the Tech lab?).
11. You still aren't making nearly enough workers.
12. Your Orbital Command was really late.
13. You aren't scouting - If you scouted at about 8:19, you would see that he has only 1 Stalker. His entire army is a single Stalker. He immediately starts warping in units after that (3 stalkers + sentry)
14. You aren't making MULEs.
15. I'm going to keep emphasizing this; you're REALLY behind on your economy (not enough workers, not making MULEs,
16. You scanned... empty locations. You should have already known where his base was by sending a single SCV to find his base.
17. You're spending money on tech, causing you to not have enough money to make units. You've got a Starport sitting useless because you have no gas, because you keep spending gas on other stuff.
18. At 13 minutes - His income: 1300 minerals 450 gas; Your Income: 500 minerals 225 gas
19. He has 2 fully saturated bases, your main still isn't even saturated.
20. You didn't drop at the 10 minute mark - you dropped at the 14:00 mark.
21. The attack... oh dear...
You dropped into his line (good)
You spent a lot of time attacking his gas (bad)
You target fired his nexus instead of the remainder of his worker line (bad)
You didn't kill the nexus when it was one second away from dying (really bad) - It died, but it should have died immediately and then you leave
You didn't get back into your medivacs and run away when his army arrived (really really bad)
22. You killed off an entire worker line (close to it) and he still has basically twice as many workers as you.
23. You expanded, and then didn't use the expansion AT ALL.
24. You're queuing hellions (why Hellions? they're bad against Stalkers)
Had had more stuff than you because he had more money than you and because he spent that money efficiently by making enough unit-producing structures to spend it. A 1-1-1 only works if it is done fast, and efficiently. Your work was neither, and it was slaughtered by a larger force of units which are superior to your Hellions and Marines.