Good for you! It reminds me a lot of my first time, except I was pretty much the only swimmer NOT in a speedo. I can tell you from personal experience that it only takes about 2 or 3 weeks at most to normalize it, but saying any more will spoil chapter 10 of my ongoing story "Becoming an Enthusiast"! If getting a more conservative pair of briefs helps you adjust better, then I say do it and never look back.
