I tried to take adult swimming lessons a few years ago and they didn't help. I can dog paddle and get around but I can't do the freestyle stroke w/ rotary breathing. Anytime I go under I hold my nose. I spent about 3-4 weeks of lessons trying to get comfortable going under without holding my nose but it didn't work. I always feel like water is rushing up my nose and I panic!
Good for you to stick with it and get good at it!