I didn't have much time to play last month, but I decided to play today, because I had a few hours of freetime. The game was against a 4k and I did only spot one possible mistake which is taking the ko in the upper left corner. I'm not really sure about that one, though. In the game I thought making points in the center would become rather difficult, because he could reduce or invade from four directions. Maybe W80 D10 was the wrong move? It doesn't look that good. He would also get a lot of ko threats if I don't ignore L17. I thought I wouldn't be able to make much points there anyway, that's why I took the ko.
Other than that, I didn't make any move that qualifies as a "big mistake", did I? My opponent left quick, so I couldn't review with him.
I feel like I didn't play bad but somehow lost anyway. I think after the ko I was maybe slightly behind, but I thought I played at least an okay-ish engame, so I can't see why I lost by 10 points in the end. Hope someone can enlighten me.
Here is the game: I was white.

Just got time for one quick comment:

Move 86 should be at A15. Then you kill him with no ko.

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I just noticed: after filling out M14 dame there is still something in the corner, because of the atari at P14 and R16... I wonder if my opponent would have seen that..

Edit:
@ Joaz Banbeck
*sigh* I'm somehow bad at killing dead groups.. But thanks, now I can see it as well.

Just looking near the end of the game --

The failed invasion at move 148 cost you more than 10 points.
Sometime before move 191 W could have played P2 for a gain of 6-10 points. B would almost certainly have treated this as sente, so those points were effectively free for the taking.
Move 230 was a pass, losing at least three points (compared to J1 for example).

Thanks, mitsun
So I actually lost the game in the endgame? That kinda sucks
Another question: While playing, I thought the situation after the two little fights with my weak groups on the bottom was bad for me, however, when I reviewed it, it didn't look that bad. Was I behind at that point?

Hope it helps.

Thanks nyuubi, helped a lot