I'm stuck and cant figure out where to go on Pokemon SoulSilver.?

I'm in Kanto, I have been to Cerulean city, Saffron city, Celadon city, Lavender town, Vermilion City, and Fuchsia city. I have no idea where to go from here. There is construction going on when I try to go to the seafoam islands, and when I try to go to Pewter city from Cerulean city, its impossible to get past the rocks. What do I do?