To go from zero to 200 miles in 12 days is a lot. If you do nothing but continue to ride it will almost surely get gradually better.

I think that selecting a saddle is kind of a hunt and peck process and counter intuitive. New riders end to think they need wide, soft saddles and more experienced riders gravitate to narrower, firmer saddles. Brooks leather saddles, which have a kind of cult following, look to be scary hard. You will find that there are a million different saddles. Somebody loves and somebody hates every single one of them. Good luck on your search.