how to make my portraits more accurate?

I want to get better at portrait drawings. ive been practicing by drawing plaster casts from reference and drawing faces from reference, but any time  i draw them from imagination it looks weird, and I don't know what the fix is. the first one is just a bunch of one-line face drawings from imagination, and the second one is an oc of mine, also from imagination.


https://ibb.co/wYTkLBZ
https://ibb.co/cQPDqtP

I guess the question is: What do you find weird about them to begin with? Especially if your portrait drawings made with reference don't give you that feeling, what's the difference between them? 

Like to me your portrait doesn't look weird  - which isn't to say there isn't any place for improvement or advice to give, but it's solid enough where there isn't really an easy-to-explain fix that'll help you elevate your work. (Esp since weird is such an abstract concept to want help with.)

Drawing portraits from "imagination" basically means, that you are following a pattern of construction for a human face, often called an abstraction. Either one, that you completely came up with yourself, just from randomly associating your experiences of drawing with the experience of looking at a reference, or that you completely learned an abstraction someone else originally came up with by heart, and most likely than either of those, a mix of both.
You probably organize your attempt of drawing a face by some vaguely culturally known pattern you saw someone else do, or you interpreted an abstraction someone else came up with along the lines of your own experience.

If you feel like you are doing a lot of practice, but your experience doesn't seem to develop the way you want it to, I would suggest you try to train one of the popular abstrations for a bit, so you have a basis to decide how much of them you want to include into your own style.
Here are examples of the most popular I am aware of. With a bit of search engine fu you should be able to discover free tutorials for each of them on the webs: Andrew Loomis, Frank Reilly, Henry Bridgman, Steve Huston, John Asaro,
or even japanese industry style, which sacrifices natural proportions for style, and is mostly shared by a lot of japanese artists, look for Manga or Anime style.
https://line-of-action.com/forums/users/190807/replies?page=4
I am a bit lazy with the links. This link should lead to old posts from me, and if you scroll a bit down you should see examples of the results these different artists are going for. Generally Andrew Loomis is the first go-to, but you might already know him. If you already know Loomis heads, but feel, like they aren't doing it for you, you can check out those other artists. Becoming familiar with more than one of them also makes you more familiar with the entire concept of using abstractions for "drawing from imagination", which can help you you reflect on your own way of drawing faces and heads.

Generally, these are all artists, that come towards drawing faces from lines. There are obviously completely different approaches towards portrait painting, like approaching from value, but unless someone insists to read me write about that, i won't, because I barely know, that they exist.