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