Analysis wrong on blunder? Is this normal

I was going over the Analysis of a Recent game ( I'm a beginner in the 600's) and I'm convinced this is not a blunder move but the start of a Forced checkmate. 

now it says Qd4 is a blunder, However, this pretty much forces a checkmate or the loss of a Queen?   ( I thought I found a brilliant move?) 

If White plays Rxd1 then I Qxb2 checkmate. 

IF white plays Qxg7 then I take the queen on g7 with my Queen on d4?

The evaluation of the move dropped a lot, from -8.8 to -1.8. so black is still better but it's not an unstoppable mate and white doesn't have to give up the queen.

Oh after an hour of reflection on this, it took me ages to post this, I think I have my answer, and of course the computer is right and I am a wrong newbie like we all where once. 

White would reply with Qxe6(check) --> forcing me to do Rf7 --> allowing white Qc8 Check __> forcing me to Bf8 

These loses my Knight , and ultimately my pin. on King . 

The game is still kinda balanced, But I fluffed a good position cause I saw what I thought was a double-protected attack. 

Oh well, One month in , things can only improve. 

Thanks a lot for the time to reply. It's appreciated. Sometimes I think all the hours of watching training videos and doing puzzles I'm starting to get there, alas what I think is a good move after consideration is still a blunder. 

It's a blunder because, white mate in 1 which is Qh7

No, it is not mate. Black has Kf7.

The engine actually recommends Rf7 instead of that Queen move, in order to meet Qh7+ with Kf8, and afterwards to take that pawn with the queen. Perhaps even more natural is to play Rf6, and after Qh7+ to tuck the king on f7, and after white recaptures on d1, not to take the pawn at all because it would blunder a queen after Bh7+, but just finish the development with Nc6, and then go from there, if white don't move the queen from h7, Rh8 can now be played for instance to chase it away.