hi itzhoyt! i think in order to measure out proportion accurately you should look up a proportion chart (you know, like 8 heads tall figure) and draw it. your sketches have a lot of potential! i think also using shapes for the main chunks of figure (head, torso, hips) will help you with structure. for limbs, try using curves (like gestural lines) instead of straight lines.
you can also improve proportion by using 'landmarks' on the figure to designate where something goes (e.g. hand is in line with face, knee is parallel to shoulder, etc.) this is useful for more complex poses. it's a little hard to explain in text.
overall, you're doing great! i hope this helped you!
