Welcome, from a perplexed forumite
5.54% does not make you pre-diabetic! Usually the number is above 5.6% (see edit) so you are close. If you are pre-diabetic (and may be you should consider yourself in that state) then the best thing to do to nip it in the bud is to lose inches from around your waist. You really need your waist to be under half your height.
A good way to lose weight is to stop eating sugar and limit fructose intake (ie fruit and fruit juices) and also look at something like the 5:2 diet to get you under way. Most of us go even further and stop eating most carbohydrates (as D sufferers they are our nemesis) and that includes potatoes, bread, rice, pizza, fruit, sugar in all forms, cake, flour,... That means no fast food: curry, fish+chips, burgers, chinese, pasta and the list goes on.
So small changes now will make a huge difference for your future.
Exercise will help to waken up your muscles to use the insulin so you do not store fat but it does not really help you lose weight. Definitely gives that feel good factor though
Hope that helps
edit: thinking about it I think the Pre-D figure used is 6% (42 mmol/mol) so you are somewhat off of it. May be your doctor is giving you an early wake up call with D diagnosed at 6.5% (48 mmol/mol). Your 5.54% (37 mmol/mol) is well within.