LaTeX Error: Command \setstretch already defined

LaTeX Error: Command \setstretch already defined

I ve got an issue :
LaTeX Error: Command \setstretch already defined.
and have got no idea what s wrong coz all was going fine. The code is
below. Thank you for helping!
\documentclass[12pt]{thesis}%{book}%{%
%\usepackage[utf8]{inputenx}
%\usepackage{savesym}
\usepackage[numbers]{natbib}
\usepackage{amsfonts}
\usepackage{amsthm}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{makeidx} %If you want to generate an index, automatically
\usepackage{graphicx} %If you want to include postscript graphics
\usepackage{epigraph}
\usepackage{pdfpages}
\usepackage{url}
\usepackage{breqn}
\usepackage{setspace}
\usepackage{dsfont}
\usepackage{eurosym}
\usepackage{epstopdf}
\usepackage{color}
\usepackage[french,english]{babel}
\usepackage{titling}
\onehalfspacing
\usepackage{everypage}
\usepackage{draftwatermark}
\SetWatermarkText{confidential}
\SetWatermarkLightness{0.9}
\SetWatermarkScale{4}
\setcounter{secnumdepth}{2}%{4}
\setcounter{tocdepth}{2}%{4}
\setcounter{figure}{0}
\theoremstyle{plain}
\newtheorem{thm}{Theorem}%[section]
\newtheorem{defin}{Definition}
\newtheorem{prop}{Proposition}
\newcommand{\eqbydef}{\overset{def}{=}}
\begin{document}
blablabla
\end{document}