Why is my PS3 internet slow?

[The Shadow™ ®]

just because you have not changed anything doesn't mean nothing has changed in your internet connection
someone might have moved nearby and have a router that interferes with the signal from yours making it worse
weather affects radio signals and that's all a wifi signal is , a change in weather can affect the wifi connection
you or someone may have gotten a new phone or another electronic items that interferes with that wifi signal
you could have gotten a virus or spyware on the laptop that changed your router settings , have you done a full scan recently ?
your router could just need to be reset
there might be a firmware update for the routers software to fix a known issue , do you check for updates regularly ?

wifi is not perfect , it constantly changes so you may need to regularly reboot the router and check its settings every few months or just get a new one every few years because they wear out