Full harddrive won't boot, broke?

I have a Macbook Pro (last version before black keyboards), and I believe I simply filled up my drive too much and now my computer won't boot up. Now that sounds silly, but it started to freeze up and I knew I had no space left.

Once I turned it off, it won't boot up. The white screen with the loading screen just appears. So I tried to "T-boot" it up as an external drive on my friends mac, but nothing shows up. His Disc Utility won't find anything once I plug my computer in.

Now, I could try to do a CD boot, but I have some files I'll be really sad if I lose on the computer. Is there anything else I could try?

Thanks in advance.