Nd4 doesn't lose a pawn due to a well known trick - Qg5 (after Nxe5)
You were right about d5 not only does it not work tactically but you shouldn't try to open the centre when behind in development unless there's a good reason for it.
Don't be too annoyed about the loss - these kind of moves are often played in blitz and the only way to get better is to make all the mistakes at least once
To keep things simple and positive, I like your thought process, and how you are checking to see which pieces and pawns are under attack. This will serve you well down the road!
Now a little constructive criticism. From the way you annotate, I'm guessing you may have read or at least heard the principle that says in the opening, "never move the same piece twice unless you have a really good reason to". On move 4. Bb5. You stated you didn't understand whites move. OK, nothing wrong with taking a few mins to think then. Is his B a problem there? Is he really threatening to take my N, and if he does will that be bad? Is my N defending anything, and if he removes my N, can I still defend adequately? If you ask yourself simple questions like this, you should be able to find a better move, and still hold fast to your opening principles, of always bringing out a new piece instead of moving one piece over and over. Perhaps Nge7, or Bg7, or even d6 (although I'd prefer one of the prior). Not that my stated move choices are perfect here...the idea is to get YOU thinking of the right moves. 
OK...On move 5 you seem to notice that you've wasted time with previous moves. This is a good observation, and having put your thoughts down like this, you will remember next time to look for developing moves, rather than repeating this mistake. So kudos on this! You are seeing your own mistakes now!
Move 7...d5 seems a bit hasty, but I like that you are interested in striking in the middle. However, another principle that should guide your opening ideas is, never break or open the middle while your K is still there. Very dangerous. Get castled first! Until then, try to keep things closed in the middle. (OR at least be sure you can get castled quickly).
On move 8 you still note that white is well ahead in development. How can you fix that?
Also, ask yourself the following questions AGAIN before moving. Does my opponent have any threats? Can he take a piece? Does he have a check? (no matter how ridiculous that check or threat may seem at the moment?) Once you answer those, you can decide if your planned moves are risky or good. In this case, finding the N check before moving the Q may have revealed the looming fork. But, don't be too hard on yourself there, because we all miss those from time to time. 
Keep practicing and for sure keep annotating your games. As I read through your thought's, I can see that you are already answering your own questions, and notice the problems your self. Keep it up!!! 
Hope this helps some.
Regards!
Thank you so much, both of you. I have carefully read through your comments and feel better already. It was very kind of you, Vladimirduce, so spend so much time explaining. Interestingly you both point out the opening of the centre being a mistake, and when I look at how it panned out, it certainly was.
This game is not my finest hour. I've tried to show you what I was thinking as black, and perhaps it was 2 unpleasant blunders, or perhaps white's good opening strategy, or perhaps my desire to do anything to avoid 4 knights again, that led to my demise here. Certainly there is a lot to choose from.
I'd be grateful for all comments, particularly ones that won't make me want to give up chess and weep in a corner.