If you could clarify a bit...
while we could argue its just semantics, to many the term "FMG" means a non-US national who trained outside of the US, while "IMG" refers to a US citizen who trained outside of the US.
In either case, IM is typically not competitive at *most* programs and if you are a non-US citizen, most of your colleages will have also trained outside of the US and whether its Caribbean or another non-LCME program, it isn't a significant difference when it comes to evaluating your application.
Finally, if you have done well in your IM residency, then there is no reason why you should have trouble getting into a fellowship; the farther you get away from your medical school in years, the less it will matter (at most places).