Is experiencing ecstasy, the discharge of fluids, and tremors when sleeping on one's stomach and touching one's chest considered masturbation, even without touching the genitals?

Lying on the stomach is forbidden by sacred law. What you mentioned about arousing yourself by touching your chest, feeling pleasure, and the emission of fluids is a type of masturbation. You must repent to Allah for it and not return to it. If you need such an act, then let your husband do it with his hand, for you are permitted to enjoy his entire body.