Generally before puberty sweat glands are not very developed.so after development of sweat glands u starts sweating from ur armpits and other area excessively.and this starts to full extent at age of 17to 18 in females.and sweat never smells salty it's due to putrefaction of sweatng products by bacteria.so clean ur arm pit shave that area frequently and wear freshly washed clothes.as per salty taste is concerned on ur tongue either u had or presently consuming excessive salts.if this is correct then limit salt intake to 1gm daily.and if u r not consuming excessive salt then go for serum electrolyte investigation and routine examination and further update me with ur reports

Since it has started few weeks back only it can be due to excessive salt intake . Otherwise get yourself tested for cystic fibrosis