Massallah pertaining to hajj and ihraam

1. During hajj, while in ehraam, is wearing underwear and vest impermissible. I have a post urine drip problem, where a few drops of urine drip after I pass water, in this situation, can I keep my underwear on. I usually keep a pad made out of toilet tissue in my underpants.
2. during salaah, does clearing ur throat invalidate the salaah.