My PS3 will not read discs?

I was casually playing MW3 and the game ended, just as usual, but the leaderboard came up and my playstation froze. i waited a few minutes, and nothing happened. i heard no strange noises, nothing out of the ordinary, and so i turned off my ps3 using the power button on the front (it is a ps3 slim and does not have a power switch at the back). it then flashed green and didnt stop, and didnt turn off, so i turned it off at the plugs. i left it a minute or so and turned it back on. i then decided i would play black ops 2, so i took out mw3 and inserted black ops 2. then my ps3 would not read the disc.. the little clock in the corner was spinning but then stopped, no option to play the game. it then sounded like the game reinserted itself into the ps3, but still nothing happened. i then tried this again several times, still nothing. it has pissed me off, i treat my ps3 with care and it does this to me :( so anyone know whats happened and how i can fix it???

- it is a ps3 slim, i cannot remember what gb it is, had it for a few years, dont think theres anything else you should know...

will really appreciate some expert help right now!!!