Paragrafi, interline diverse

Salve,
piccolo problema
quando do una linea vuota mi vengono creati dei paragrafi nuovi, fin qui ok. il problema è che tra un paragrafo e l’altro l’interlinea cambia. in alcuni casi il testo va a capo e c’è il rientro (quello che voglio) a volte invece, va a capo, lascia una riga vuota, e fa il rientro.

capita solo a me?

questi sono i package (anche togliendo verbatim non cambia)

`
\documentclass[a4paper,openright,twoside,11pt]{book}
\usepackage[english]{babel}
\usepackage{phdthesis}
\usepackage{graphicx}
\graphicspath{{img/}}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{amsthm}
\usepackage{color}
\usepackage{url}
\graphicspath{{img/}}
\usepackage{titlepage}
\usepackage{graphicx}
\usepackage{listings}
\usepackage{fancyhdr}
\usepackage{verbatim}
\usepackage{makeidx}
\usepackage[colorlinks=false]{hyperref}
% bibliography web (not used)
\usepackage[resetlabels]{multibib}
\newcites{web}{Web Sites}
% cite ref
\usepackage{citeref}
\renewcommand{\bibitempages}[1]{\newblock {\scriptsize [\mbox{cited at p.\ }#1]}}
%listing
\lstdefinestyle{JAVA}{
language=JAVA,
basicstyle=\scriptsize\ttfamily,
numbers=left,
numberstyle=\tiny,
stepnumber=1,
numbersep=5pt,
tabsize=1,
extendedchars=true,
breaklines=true,
keywordstyle=\color{red},
frame=b,
stringstyle=\color{white}\ttfamily,
showspaces=false,
showtabs=false,
xleftmargin=17pt,
framexleftmargin=17pt,
framexrightmargin=5pt,
framexbottommargin=4pt,
commentstyle=\itshape\color[gray]{0.3},
stringstyle=\itshape\color{black},
keywordstyle=\color{black},
moredelim=[is][\underbar]{>}{<}, backgroundcolor=\color[gray]{0.95}, showstringspaces=false } \lstdefinestyle{XML} { language=XML, basicstyle=\scriptsize\ttfamily, numbers=left, numberstyle=\tiny, stepnumber=1, numbersep=5pt, tabsize=1, extendedchars=true, breaklines=true, keywordstyle=\color{red}, frame=b, stringstyle=\color{white}\ttfamily, showspaces=false, showtabs=false, xleftmargin=17pt, framexleftmargin=17pt, framexrightmargin=5pt, framexbottommargin=4pt, commentstyle=\itshape\color[gray]{0.3}, stringstyle=\itshape\color{black}, keywordstyle=\color{black}, moredelim=[is][\underbar]{!}{?}, backgroundcolor=\color[gray]{0.95}, showstringspaces=false } \usepackage{caption} %listing 2,caption \DeclareCaptionFont{white}{\color{white}} \DeclareCaptionFormat{listing}{\colorbox[cmyk]{0.43, 0.35, 0.35,0.01}{\parbox{\textwidth}{\hspace{15pt}#1#2#3}}} \captionsetup[lstlisting]{format=listing,labelfont=white,textfont=white, singlelinecheck=false, margin=0pt, font={bf,footnotesize}} \makeindex `