Dear Corsi,
the nitro helping so much is a very good sign that LIS will work for you. Dont be pessimistic - all of us who have had LIS havent any regrets at all - and even if it doesn't cure you 100% (which I'm sure it will, by the way!!) the relief you get from that tight feeling makes it SOOOO worthwhile.
Once its all over, you will be happy! xx