Power went out and my Imac won't reboot

So I was working on my Imac i bought last year and the power went down a few times.

After the first time i rebooted it and it worked normally.

so then the power went out again and i waited with rebooting till the power problem was solved.

When i tried to turn it on again, It played the sound of starting up and it shows the white screen with the logo and the swirly rotating thingy

but then a gray loading bar comes and it takes about 15 minutes for the bar to be full.

then he just shuts down again.

Tried to turn it on several times. Same thing keeps happening.

Tried to get the power cord out and stuff.

not working.

Please help me.

I got deadlines