Un petit problème sous Latex

\documentclass[12pt,a4paper,oneside]{book}

%----------Les usepackages----------------------
\usepackage[utf8]{inputenc}
\usepackage[francais]{babel}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[Lenny]{fncychap} % Lenny, Conny ,Bjarne, Rejne, Glenn, Sonny
\usepackage{fancyhdr}
\usepackage{fancybox}
\usepackage{shadethm}
\usepackage[all]{xy}
\usepackage{colortbl}
\usepackage{lastpage}
\usepackage{amscd}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{latexsym}
\usepackage{mathrsfs}
\usepackage{float}
\usepackage{wrapfig}
\usepackage{color,framed}
\usepackage{graphics}
\usepackage{graphicx}
\usepackage[left=3cm,right=3cm,top=3cm,bottom=3cm]{geometry}
\usepackage{ulem} % pour les textes souligné
\usepackage[colorlinks=true,linkcolor=blue,urlcolor=violet,bookmarks=true]{hyperref} % pour les lien url
%\usepackage{setspace}

%---------- LES-COMMANDES --------------------------
\newcommand{\thecompte}{\roman{compte}}
\newcommand{\K}{\mathbb{K}}
\newcommand{\N}{\mathbb{N}}
\newcommand{\Q}{\mathbb{Q}}
\newcommand{\R}{\mathbb{R}}
\newcommand{\C}{\mathbb{C}}
\newcommand{\implique}{\Longrightarrow}
\newcommand{\equivalent}{\Longleftrightarrow}
\newcommand{\reunion}{\displaystyle\bigcup}
\newcommand{\intersection}{\displaystyle\bigcap}
\newcommand{\vers}{\longrightarrow}
\newcommand{\inter}{\cap}
\newcommand{\union}{\cup}
\newcommand{\A}{\forall}
\newcommand{\E}{\exists}

%---abreviations-----------------------------------
\usepackage{ntheorem}
\theoremstyle{break}
{\theorembodyfont{\upshape}
\newtheorem{exo}{Exercice}}
\newtheorem{theo}{{Th\'eor\`eme}}[chapter]
%document

\newtheorem{definition}{{D\'efinition}}[chapter]
\newtheorem{prop}{{Proposition}}[chapter]
\newtheorem{cor}{{Corollaire}}[chapter]
\newtheorem{lem}{{Lemme}}[chapter]
\newtheorem{rmq}{{Remarque}}[chapter]
\newtheorem*{proof}{{Preuve}}[chapter]
\newtheorem{ex}{{Exemples}}[chapter]
\newtheorem{prt}{{Proprietes}}[chapter]
\newtheorem*{nota}{{Notation}}[chapter]
\DeclareMathOperator{\e}{e}

%----En t\^ete et pied de page ------------
\pagestyle{fancy} \fancyhf{} % efface tout ce qu'il y avait avant
 %\fancyhead[LO,RE]{\leftmark}
 % LO = gauche/impair ; RE = droite/pair
\fancyhead[RO,LE]{\rightmark} % RO = droite/impair ; LE = gauche/pair
\fancyfoot[C]{\thepage} % C = centré
\renewcommand{\headrulewidth}{2pt}
\renewcommand{\footrulewidth}{2pt}

%-----------Titre-----------------
\title{\begin{normalsize}
Universit\'e \\

\end{normalsize}
\vspace*{6cm}\\
%\begin{Huge}\textbf{\color{blue}X}\end{Huge}
\vspace*{2cm}

\date{\today}}}

%----------Document--------------
\begin{document}

\maketitle
%\clearpage
\tableofcontents
\maketitle
\clearpage

\addcontentsline{toc}{chapter}{Introduction}
\chapter*{\textbf{Introduction}}
\vskip 1 cm
bla bla

\begin{prop}
bla bla
\end{prop}


\end{document}
\newpage