Not at all.
Postmodernism is the latest apologetic extension of the communist/socialist ideals that have always proved to bankrupt in application. It is actually a label for ignorance. Postmodernists are afloat in a boat without sails, yet, to their mind, should control everyone's destiny. All the way down to Davy Jone's locker.
Welfare liberalism, or plain "liberalism" as described in the U.S., is the choice of class over the individual. It could be racial, economic, national origin, whatever, but the group definition is always more important than the individual in all aspects of life as they see it. It is, by definition, the choice of dependencies over individualism. They cannot be post-racial as they define everything in terms of classes, including those of race.
I don't use them interchangeably, but, for all practical effect, the modern American liberal's roots derive almost entirely from the emptiness of postmodernism.
Conservatism is not the opposite of liberalism as it is defined here. Libertarianism as used here is a purer definition of the opposite of welfare liberalism.
Dr. Paul advocates a form of libertarianism, but I am not familiar enough with his version to comment more without reading his position documents. Which i shall attempt to include in my busy schedule after I get back from a long overdue bike ride this evening!
Of all the choices in definition, I prefer classical liberalism, which provides more of a balance between the real and the ideal. It is too bad that the use of that word has been co-opted.