MSTER232, I've had a look at some of your drawings and by taking one in particular, I feel I can offer some advice which should hopefully improve your work (and many others') in the future.
What strikes me about your drawings is that the perspective seems to be a little off in many of them, by looking at the guide lines I have added above you can see what I mean. You said yourself that the right headlight is higher than the left, but you can also see that the base of the windscreen and both grilles are not level, and the left tyre is higher than the right, to name but a few. I know these errors are minor, but if they are out by the tiniest amount it spoils the drawing. It can help to lightly draw lines like these when making the initial sketch, but this
must be done before adding any detail to the image.
By the way, this is fantastic advice, and something I also do myself.
At 1ness
i can't strongly recommend enough by using a mirror to check your sketches whilst doing them to check for perspective errors etc.
This is an example of one of my drawings when I haven't applied these techniques:
I drew this when I was bored at work, it took about half an hour. It was drawn in biro on the back of a notepad, so I could not sketch any guide lines because I couldn't erase them if I did. As a result, the right headlight is smaller than the left. Getting the perspective wrong caused the knock on effect of making the width of both the number plate and the left headlight/bonnet line a little out, and my errors are clearly visible.
Another thing I noticed is that it appears you smudge larger areas to add shade; avoid this, as it makes the drawing look less defined. Draw any shading carefully instead, and you'll instantly notice an improvement.
It helps to be a perfectionist when drawing. Look at every little detail on the car, ask yourself if it looks exactly like it does on the image from which you're copying, and do it again if it doesn't. For this reason, the front wheel on the Alfa 8C I posted earlier will have taken me several hours alone, because I wasn't happy with it. Frankly, it drove me mental to get right.
By the way, I'm not picking on you! Given your age these drawings are pretty good (especially the Subaru pic!), I'm sure that if I dug out some of mine from when I was young, yours would stand up very well to them