How Can I Fix My Ps3's Internet?

Ok, Whenever I play some call of duty or GTA on my PS3 it always has extreme lag. Now I noticed this only happens when someone is on the computer at the same time as im on my PS3, which is a problem because my dad is on the PC 24/7. Now im not sure if my PC is connected to my wifi or the landline. But what i did was just go to "Network and Sharing Center" and disable my wifi. The weird thing is it says its connected to my wifi still but has like a Ethernet cord symbol. It still lags, is there any way i can fix this where as i can go on my ps3 while my dad is surfing the web?

Suggestion:

It is to do with your router rather than the pc or ps3. Theres something called QoS (Quality of Service) that basically shares the internet connection more fairly. e.g. Someone that is say download a game demo from the ps3 online store is going to want more bandwidth than the person surfing the web and not downloading anything. Without QoS setup, if you do the same scenario, the PS3 user would use all of the bandwidth but the pc user will not be able to load any webpages at all.

Sorry for the long winded explanation but i tried to explain it as simpily as i could