Ways to get your credit up quickly ?

 i’m trying to get my credit up to buy a house before my baby is born in March… I got preapproved with a cosigner from one place and another place that if I wait two months I’ll be able to get it by myself and that would be the FHA loan so that would be a lot better for me.  but I didn’t know if I could get my credit up quicker? I have a couple of credit cards that I have combined into one payment that I can’t use. And I have another one through my bank that I’m paying off.