It's your job. Your employer is your boss. Within reason, he will dictate your job and hours. He will tell you what to do. He will tell you when to do it. He will tell you when to eat lunch. The life of an employee has been like that for a loooooong time. No one is making you stay at your job. It's time to look at life like an adult, be thankful that you have a job.
45 hours a week for most professional jobs is normal. Most businesses that require that of employees are not monopolistic, and as long as they pay overtime, they are within legal grounds to require it. However, if employers are making unreasonable demands or demands contrary to employment contracts, it is very important for individuals and groups of employees to take the lead in denouncing unjust practices.
1) What does your contract say? If you do not have a contract, you do not have an argument.
2) What are the labour laws in your country? Your profile says Paris, so I am assuming Paris, France and not Paris, Texas. Most of the users here on ASK.com are Americans, with another good percentage from Canada, UK, Ireland, Australia, and India. We are not familiar with your laws and cannot advise you.
No I wish I could work 45 hours a week I work on a farm 70-80 hours a week thats seven days a week and I dont get paid overtimefarmets arent required to pay it. So all you people out there that bitch because you work a little overtime try farming for a month you will like your job a whole lot more