Acer Aspire 5741a, Sound jack problem?! HELP?

I have a 4 month old Acer Aspire 5741A laptop. The headphone jack was working fine until a few weeks ago, now when i plug it in, i can't hear nothing but the speakers of the laptop are working perfectly, if i adjust the wire of the headphones to a certain position, which is slightly pull back the wire towards myself, I can then hear some sound but when i make the slightest movement, I'm back to square one, I have tried different headphones that are working on my brother's laptop on this laptop, still the same problem. HELP!?