We've never had a problem not having pills in the original packaging. We both take one of those one week pill thingies (showing our age here) with medications & vitamins already sorted and not actually in any container to speak of. My wife also throws things like aspirin, vitamin C, Tylonol, cold pills, etc. (the just in case stuff) loosely in a zip lock bag to save space. This is always in our carry-on and we have never had a problem or even been questioned on it in 8 trips.
IF you were to be questioned it would be most likely to happen on your way back into the US not into Jamaica. If you take a supply to last you the time you are on the trip you can be pretty certain you aren't going to be questioned. Not doubting rjammin's statement just saying that getting back home is where you'd most likely encounter more scrutiny if it were to happen...and it certainly could. Most pills are marked in some way...for example Tylenol is readily identifiable by anyone who knows what to look for...so perhaps it wouldn't be an issue with most things except perhaps supplements which aren't always so clearly marked. I take travel size bottles of Advil, Tylenol, etc and I do bring my prescription bottles just in case, I figure I'm not brining that much so they don't take up that much room in the suitcase if there is any chance it might save me any questioning it's worth it. Guess unless you know someone who has experienced a problem or someone working in the "industry" there is no good answer.
I have never had an issue with vitamins or any of my prescription meds. However, just recently I read about a break in at a NON Couples resort. The guest had some schedule 2 prescription meds taken along with money and electronics.
She did have a note from her Doctor stating what the meds were for along with the Doctor's contact information so they could be replaced legally. I always travel with my meds in the original bottles but never thought of taking a letter just in case something happened.