Don't change a thing...I have been travelling solo to Negril for years, though I now have friends and "family" there. I agree with the others, set up a driver so when you arrive in MoBay, you will be set. Your initial exit from the airport is the only thing that you may find a little intimidating...I know I did. Its a little culture shock mixed in with lots of men trying to get your attention (for lots of different reasons....) Don't get me wrong, not scary, just a really busy area.
Once you are in the car and heading down the road, relax, enjoy the ride, stop for a cocktail and enjoy the views!
A couple of days alone will give you a great opportunity to unwind. I really don't think you will feel lonely, I never have. CoCo is a nice spot, lounge and sunbath during the day, and enjoy their bar/restaurant in the evening (if you don't want to venture too far).

I am heading to Negril on my own in 3 weeks, looking forward to every minute of my "me" time!