@ketamine_dragon Perhaps consider setting up your light source on the still life scene with purpose to maximize your ability to identify a clear differences between the highlight, the half tones in the light family, the core shadow and the reflected light (also part of shadow family) on the different planes of the objects. Traditionally this is done with a single dominant light source positioned such that it is above, in front of and to one side of the objects (sometimes called Rembrandt lighting). This approach gives great insight into form shadows. Try this out in a dark room and aim a single light at objects, and it will become clearer for sure. Ask yourself when looking at each plane of an object whether it need be depicted as highlight, half tone, core shadow or reflected light, and draw accordingly with your decision. If previously you have been drawing still life lit by multiple light sources from different angles which are flooding light on scene, sort of the equivalent of in most photography of fashion models which aim to eliminate shadows on faces for instance, then that makes distinguishing shadows way more frustrating and challenging. I hope that helps.

I agree with Lydia, but will expand on my impression. In addition to overall liking your subject and composition, definitely good, my first thought was to look for the bounce of reflected light, like from the floor under her bosom or her chin. It's subtle, but here, it would really enhance. You have already done a lot of effort on your light, but it also casts deeper shadows, too. Look to play up colors even in shadow values. Light isn't just orange, but a hue of lighter value of what object it is revealing, too.

Can I oil paint without solvents as I have no ventilation.