So I followed the video a few times, and I tried practicing with a ref , here is a side by side comparison with grid
and without grid. My question is why does my head look so different from the ref, what am I missing or what can I do to improve ? 
practise / developing your artistic eye, i used https://thevirtualinstructor.com/, for maybe 2 months and its crazy how much i improved just by changing the way i look at things. Im pretty sure CGcookie also has some tutorials or posts on the subject,
Oh I bet stuff like facial hair, eyebrows, lashes, actual hair on the head and the eyes, with the iris and all that stuff, I bet it makes a huge difference. And of course having the camera view in orthographic and perspective also makes a huge difference. So I guess maybe when you add all that stuff your sculpt will resemble much more closely the reference. And the sculpt is looking so awesome, love the crisp and well defined shape you got going there Aneeqa.
Yeah I think I need to keep practicing to develop my eye, and yeah maybe with hair eyebrows added it will look more closer to the person
Along with Omar's suggestions, I'll bet your head isn't as far off as it seems in the images. Light your head the same as the reference and it'll look much closer.
But the problem you're describing is common with folks trying to "xerox" a reference. This is why I gave the method up, especially for real likeness (I like to do it for stylized). Because when you matches facial landmarks so well, as you've done, but you stand back and it still doesn't look right - what more can you do? Though perhaps unintuitive, I've found that developing my eye by avoiding xeroxing has made my likeness sculpts better.
I think adding the lighting will make a big difference to how you see it.
It looks awesome to me, the only thing I see different is above the eye, it looks a little too inflated. You probably see it that way because of the shadows.
I would add a light top right and slightly in front off the model. And perhaps a fill light to the left as we look so the left side (as we look) is not to dark.
That should help.
Hair and other details can make a huge difference. Imagine how different you would look if you shaved your head. I know, my hair hardly grows anymore 👴