I'm 5'11 too, and what I did was hit the sales at JC Penny for shirts and for bottoms I mostly did stretchy skirts, because finding maternity pants that were long enough was a chore and when I did they were outrageously expensive.
I was pretty comfortable my whole pregnancy doing that. Hope this helped!
Also-check Craig's list. When I was on the site I saw a woman in my area selling all her maternity clothes for great prices-why pay a lot when you know you only wear them for 9 months?(unless it's something special your going to-and even then you might find something!)