Stop sign when turning on macbook pro

My macbook pro was running very slowly, sometimes not loading web pages and always crashing, I decided to upgrade to Yosemite, it made it worse for a few hours but then suddenly my macbook was running quickly and normally, I thought it was fixed. Today I kept getting the rainbow pinwheel, every few seconds, I had to restart my macbook several times (this took ages as there is a loading bar when I entered my password) but now I am just getting a weird grey stop sign and I am unable to sign in or even get on my macbook. I should also note that the fan was very loud these past few days, now I can't hear it at all.

I have only had this macbook for about 9 months and don't have the money to get a new one, is there anyway to fix it at home, or will I have to take it into a store?