The bike fit is the way to go like Anthony said. It also never hurts to keep working on the core, not that you have a weak core, but you can never get enough core.
Its hard to say about raising aero bars without seeing your setup, what I did was actually move the aero bars towards me, so that I was less aero but more comfortable, making sure my elbows are right under my ears. That may actually put you in a more powerful position, meaning if you had a watts meter you may generate more power. I did also move the seat up a bit, just a tad. Typically the more aero you go, the less power you produce, and less comfortable you are (at least in my case). Strange, but true. However I'd always take power and comfort over aero. Your doing an ironman if memory serves, so you need the comfort.
Its impossible for us to tell if we don't see your position. And what worked for me isn't going to necessarily work for you. If the bike fit is out of the question, only thing to do is experiment yourself.
