Do you have Diabetes??? You said you have a meter, but none of your meds are diabetic meds. I have Type 2 and I can tell you a few things that could help you.
First, your sugar should not be fluctuating like that, but since you said you test 10x/day it could just be that you are not testing properly. You should test before your first bite of every meal and again 2 hours after that first bite. (Not 2 hours after you finish). Also, first thing in the AM and last at night. That will give you a better idea of your sugar levels. A good blood sugar range for a diabetic person is 70-110 (some docs will even say as high as 150) before a meal and under 200 2 hours after you start the meal. 598 is wayyyyyyy too high. If you are testing correctly, you need to run, not walk, to the doctor and get some blood work done to check your A1C level (3 month average of blood sugar level).
Another thing to consider, is that a lot (and by that I mean most) people don't correctly count sugars or know what is or isn't actually counted toward sugars. You said you were really strict with your carb intake, but are you counting hidden carbs (artificial sweeteners, certain protiens, fruits & milk sugars for example)? You can check out this site for more info on hidden carbs. http://wilstar.net/lowcarb/hiddencarbs.htm
Also, oral steriods (prednisone) are known to affect blood sugar. These steriods have a history of raising sugar levels in the blood. Does your rheumy know that you are diabetic? I won't let my dr's put me on steriods unless it is absolute last resort and only for short amounts of time then because it will blow my sugar up sky high too. If you are doing the first two steps (blood checks and carb counting) correctly, chances are, it's the prednisone spiking you and you might need to find a non-steriodal switch for that med.
I have also found that stress will raise (or dramatically drop) my sugar too. Please don't wait 3 weeks to get this resolved. I know how much you want to enjoy your big day, but this is a life or death type of serious matter. Unsresolved, high blood sugar is related to heart attacks, strokes, liver or kidney damage, blindness, and death. If you are taking birth control, your risks are more elevated. I am assuming that you are honeymooning after the wedding and that will probably involve a flight to some location away from your home. That is the last place you want to be in medical emergency, so please, call your doctor today. If they won't take you, go to the ER.
Best of luck to you!