I'm not sure if I'm posting this to right box thing but over the past few days the internet and the wifi lights on my nans modern have been flashing and my nans internet is slower then a snail and it effecting YouTube and similar sights . I've try the off and on again thing but that hasn't work its seems to have made worse help
Are you testing speeds over wifi or connecting via a wired connection? Test on wired connections.
What results do running a speedtest provide (google speedtest) - upload and download and ping?
What NBN speed are you paying for (12, 25 or 50 Mbps)
What NBN technology is your house using (FTTC? FTTN? HFC?)
What is the internet light on your modem doing (colour? flashing?)
The "tried the on and off thing" should probably have suggested that to me. (Although as an IT professional the "on and off thing" covers about 50% of issues.
You need to contact Optus directly. Phone (bit slow) or LIVECHAT here online 24/7 (faster).
Ask them to test the line speed between Optus and your modem. They will either say its running real slow or its fine. If its fine then the issue is likely in your house. If its slow then the issue is either Optus, the Optus modem or NBN wires. If Optus can't readily talk you through an answer they will either a) Send out a replacement modem, or b) ask NBNCo to investigate.
See where that leads.
PS I would also just run a speedtest on your equipment. Simply google SPEEDTEST and choose one to run. It will tell you how fast your connection is.