Headphone jack problems

I have had my computer since june and everything was working fine. In September my headphone jack stopped working. I bought an adapter so I can try to plug my headphones into my smaller jack but its not working yet my speakers still work. I tried following some of the previous comments and how my audio sounds horrible. I really need your help because I need my sound working properly for an assignment I have due in a few days. Thanks!

If you need any info about my computer just let me know where to find it.