I am by no means an expert on the Najdorf (my experience is entirely on the white side, and some time ago), but it looks like you lacked the urgency and dynamism that such a double-edged line requires, and didn't know what your plan should be (no, Black should not be attacking on the kingside after white plays O-O-O) or even how to inconvenience White at all.
A few moves jump out at me as being either inaccurate or outright wrong:
8...Bd7. Maybe theory knows better than me, but this looks like it just gets in the way on d7. That bishop wants to go on b7 if you ask me. I'd want d7 for the knight (which noticeably stays on b8 for the whole game).
10...Ne8. This is an odd move, and the strategic plan behind it is wrong - Black is never attacking on the kingside in this type of position. That knight is covering the d5 break and eyeing e4 (making it harder for white to throw the f-pawn up the board, which he later does with impunity). You shouldn't be moving it away until White's g-pawn gets rolling, and then d7 would be preferable to e8 (another reason not to put the bishop there).
And, as others have mentioned, 12...Bxh4 is a suicidal move that just opens up lines against your own king. The pawn is worthless - this is not a position for pawn-counting. Someone is getting checkmated before move 35.
Really, you needed to get some kind of counterplay on the queenside and centre, for instance, at some point pushing b5-b4 to kick the Nc3 away and playing ...d5. Black's central strike is often the antidote to white's kingside shenanigans in the open sicilian. You never played ...b5 at any point, even though the presence of a bishop on c4 makes it basically a free move.
I'm not sure what to suggest, really. Everything about this game suggests that the Najdorf is really not the opening you should be playing, and I'd recommend you take up 1.e4 e5 instead. At least, get a basic primer on the sicilian, such as "Mastering the Sicilian" by Danny Kopec. This covers the basic ideas in open sicilian positions without getting bogged down in theory.
And study some master games. The problem isn't that you played one or two wrong moves in this particular game, the problem is that you don't appear to understand at all how the Sicilian is played.