-Update OS X to 10.10.4 if you haven't already.
-Reset your router, it may be one device TODAY, but the router could be having an issue(and if it is, no matter what else you do, the issue will still exist)
-IF after doing both of these things, restart the computer holding shift to boot into Safe Boot. Please test for the issue there, if it is occurring still it is likely OS X related, if the issue goes away in Safe Boot then it most likely is a piece of software that has been added to the computer. I can assist further beyond this, but since we are talking about several different variables, do the steps above, and that will eliminate at least two of them.
-Please post again if the issue continues, and let me know if it is or is not happening in Safe Boot, and I will help you from there.