Hi Kits,
You have just discovered one of the "joys" of the internet
It can be caused by many things.
First of unplug all connections and have a bit of a look and give them a quick wipe....any new moisture or corrosion etc.
That may work........
But my bet it's a bit further up the line and will be a problem with your isp, quite possibly in the cabinet or one step back from that at the exchange.
Have you had a lot of rain lately ?
Anyway best way to get this sorted is to give your isp a ring .....with some luck you will not have an Indian call center.
No offence to Indian folks but a call center that uses voip coupled with a strong accent and very little knowledge beyond the script they follow on their puta makes for fun conversations......
Unfortunately Kits theres two types of internet users .... those that have been through this and those that will 8-P
If it's within your current tech ability you could try resetting your router, it'll be on the call center staffs things they will talk you through otherwise.
Basically check as much of the hardware at your end that you can, then hassle your isp ..... and don't give up till problem solved.
Enjoy !!