Usually about 4-6 weeks is good. The burning sensation is normal. There should never be blood when stretching. That means you've tore the fistula and it could cause scar tissue making further stretching more difficult. A good hot shower will help with "loosening" up the skin to stretch easier if you're doing it yourself. A good reputable piercer can also do it for a small fee usually.
PS. 9 years of being a professional piercer.. just so no one thinks im just talking out of my a..