1st home purchase! Credit questions?

I am trying to gain 100% financing to purchase my first home In NC. I applied at my credit union and was approved for 95% financing due to my limited credit history. I do not have any installment payment history. I do have active revoloving credit x5 which I have never been late on but have only have had for 6 months to 1 1/2 yrs. All balances on the card are at or below 50% of the the limit. I am not sure of my credit score but was told by the CU I applied for the loan at that it was not the factor in the approval or non approval of the loan. My question is... what do I need to do to improve my credit history? I do not need a new car and according to the CU I would probably not qualify for a personal loan either since it would be unsecured. I do not have enough for a down payment. Please Help! I would like to purchase by Nov-Dec. of this year.