Zofran for nausea just not cutting it.

I have bad nausea and I took a zofran (what my doctor prescribed) and it was ok for maybe a few minutes. It's the 4 mg ones. Then later this night I felt it again and took it. Then I threw up. 😑 then I layed in bed feeling nauseous still. Is it bc I threw up right after I took it or what? Am I still feeling it bc of the dosage? Should I try to switch meds? I can't swallow pills so the dissolvable tablets is all I can do rn but they only work for a bit. And they make me constipated which really doesn't help my situation here 😤🙊😩😷 What is happening to me? Why am I always nauseous! So many questions that nobody will answer! Starting to feel hopeless here...