I sleep early with the intention to get up early for fajr so when I sleep I get bad images of opposite gender while I close my eyes and it continuously comes in my mind so I open my eyes often and it gets late to sleep and tough to get up in the morning.

When you go to bed, try to take a book with you to read. Any book. Start reading after all the recommended zikr (Shahadt, Ayat Al Kurssi, 3 times surat Tawheed and Tasbeeh Bibi Zahra).
You will sleep without any problems.