Where do i go for a DNA test?

so my birth certificate says frank is my father last time i saw him i saw 2 years old but i know he's tall and has curly hair well im very short and have straight hair anyways my mother told me that someone else could be my real father he's short and has straight plus he has the same nose as me and so does his kids .So we want to take a DNA to find out if he is my father but where do we go to take the test? can we go to my OBG doctor? and will my medicaid pay for it? i really want to find out if my father has been in my life this hole time