photos take so much space on icloud .

i have the 200 gb plan on icloud and ive checked it today to see how much space is left for me , and found out that 120 gb is taken by photos , i dont have that much photos and i dont delete from my phone when its backed up , ive checked iphone storage and it says that i have 2.6 gb of photos , how is this possible that photos take this much space on icloud (120gb) , does anyone know what is happening ?

thanks