Well, I am no expert, but I can tell you that when you are finally able to breath a little better you will be very surprised at how much that will settle you entire body down a bit. Deep breathing in the plane and in freefall calms me down alot. Also, you might want to consider what you had to eat before your jump. I know it sounds stupid but if my blood sugar is low, the adrenaline seems to have more of an effect on my body: getting the jitters and feeling tense. I always have a soft drink with sugar and caffeine in it right before I go up. I would recommend trying this before any kind of medicine but thats just me. Hope this helps.
Oh, I almost forgot, CONGRATULATIONS on your first jump!