You may not have a router problem. It may be a line problem.
Before going for a new router, try plugging your computer directly into the phone test socket (remove the cover of the phone socket and the test socket is behind that)and running for a while.
I had a similar problem and found that, by doing that, the fault was not in the router but was in my wiring. A new piece of electrical problem nearby was causing my woes. A better quality cable and a slightly different route cured that problem.
And it was cheaper than a new router!