Refinance Mortage

will my bad credit affect my husband has good credit, when he attempts to refinance his mortgage?
I have bad credit, My husband has great credit. He seeks to refinance a home he bought before he married me and wants us to apply for a refinance loan together, I'm afraid, this will affect his chances of getting a good interest rate. Also, he bought a car and when we got married, I was responsible for the payment of remuneration. It has been a whole year, and payment has always been on time but again the loan is only under his name. Is it possible to add my name to the loan with out affecting or Changeing rate in order to build up my credit? I have paid for everything on my credit report except for 4 items. This includes 1 hospital bill, 1 phone, 1 power and 1 month rent. Total represents about $ 1,600. is there hope? any ideas or links?
Just do it in his name – You can be on the title, but makes the mortgage in only his name