Can somebody help me w/ my macbook plz?

when i turn on my macbook it loads like it normally would but it gets stuck on the blue screen i tried booting in safe mode and i logged in but then it goes to the blue screen for 5-15 mins and then makes me log in again. i have tried the p+r+cont thing and holding the power on till it beeps and holding s+command or what ever the right ons were(i googled it and tried everything anybody said) nothings working how can i get it to boot????