Imac wont read certain disks

Hi, i have a 27 inch imac purchased end of 2010

Model Name: iMac

Model Identifier: iMac11,3

Processor Name: Intel Core i5

Processor Speed: 2.8 GHz

Number Of Processors: 1

Total Number Of Cores: 4

L2 Cache (per core): 256 KB

L3 Cache: 8 MB

Memory: 4 GB]

OPTIARC DVD RW AD-5680H:

Firmware Revision: 3AHB

Interconnect: ATAPI

Burn Support: Yes (Apple Shipping Drive)

Cache: 2048 KB

Reads DVD: Yes

CD-Write: -R, -RW

DVD-Write: -R, -R DL, -RW, +R, +R DL, +RW

Write Strategies: CD-TAO, CD-SAO, CD-Raw, DVD-DAO

Media: To show the available burn speeds, insert a disc and choose View > Refresh

Basically the problem is the imac will only read certain disks. It will read blank cds, written cds (audio and data) and blank dvds. However if i insert a written dvd a film for example the drive spins.. then stops and continues to do so for about 20 seconds. It also does this with all game dvds. i have tried using onyx as someone suggested i do this to rest my catches but it doesnt seem to of made a difference. My mac hasnt been moved, dropped or changed in any way recently so im not sure how the problem has developed.

Does anyone have any ideas as to what the problem migth be? I'm getting really frightened in case the worst should happen and it wont be able to read the os install disks 😟