You didn't go near his base until 25 food.
I know it's just AI which does the same things, however if you need to learn one thing it's scout > react. Send your first overlord to his base, he won't have anything that can kill it that early, you can even avoid a single marine easily, just float off the cliffs, send a drone when you build your second overlord and scout around his base, check what he's doing, regardless of what you know already or that you won't learn anything, it's practise for online play where you can't know what people will do.
A few things I can comment on.
1. You built an expansion but didn't have any drones on it for over a minute.
2. You stopped drone production for over 5 minutes and built 22 lings for as far as I could tell no reason at all, you were attacked but you had no way of knowing that was coming.
3. You had 2 lings on each Tower, waste of resourced.
4. You built a second extractor in your main but never used it.
5. You didn't see your opponents base for over 20 minutes, until you had built up a maxed army.
That last one is the kicker really, you just can't do that in online games unless you come up against someone doing the same thing for a few reasons, 1 it drags games out, 2 you don't learn much and 3 if your opponent scouts you lose.
Plus points, your lava injects were good, as was your creep spread, my only bit of advice on creep would be to work on connecting your main to your natural first.
To be honest my main criticism would be your play didn't seem to have any direction, all you were doing was massing units which is a strategy, sure, it relies on too many things, namely your opponent not doing anything.
One of the hardest aspects of SC2 for me was always just attacking, I was always too scared to just go kill my opponent, I would think "I could attack now, but I'll just get that next upgrade and another bazillion colossus, then I'll be safe". What I dis to get around this was just attacking, simple as that, once you've got a few units, run to their base, throw them at them, if you see you are outnumbered, back off and reassess and react to what you learned, for one it makes game loads more interesting and you learn loads from it.
So my advise for now, go here:
http://wiki.teamliquid.net/starcraft2/Zerg_Strategy
Pick a strat you like, maybe a couple or one for each matchup, practise them vs the AI and try to attack with them before the 10 minute mark in every game, even if you don't have enough units to with a battle, just wander to his base, engage his forces and go from there.
Once you've done that, start playing online, you can't play the AI forever, it will get you into bad habits and you won't improve.
Oh before I go, one thing to do as well is to find a "favourite" pro player, this gives you a few options, mainly it lets you develop a play style because it's easy to copy something you think is good, for me it's ogsMC (I play protoss), watch their replays, copy their plays even if you screw up, it gives you a nice baseline to work on.