average length of pregnancy is 28 days so its its only been 3 weeks theres hope yet. ive never had dropsy thankfully but your Platy
does look to be especially bloated.
here is a paragraph i found about dropsy:
The term "Dropsy" describes the symptoms of more than one kind of disease, but all of which share the same external symptoms of a bloated body with distended scales. The accumulations of fluid within the body causes bloating, that becomes more severe in a short time. The scales stand away from the body instead of laying flat in the normal way. As the disease progresses the eyes will be affected, causing them to extend out away from the sockets. The percentage cure-rate with these conditions is very low, and ultimate death is the most usual outcome for the affected fish. Although dropsy is widely regarded as a non-infectious condition, it is a wise policy to remove an affected fish away from the healthy stock. If the sick fish should die where other fish may peck at its corpse there is a chance the problems could be passed on, depending on what the causative agent was in the first place.
from the picture the scales and eyes look fine. it also says, as you will see, that its not contageous, so those both point in the direction of it not being dropsy.
i really hope its not. i will keep my fingers crossed for them