Q: bluetooth connection stops and lags

the bluetooth connection between my imac and both my keyboard and mouse will randomly stop for about 15 seconds, theyre not being disconnected because when the connections stops and say im typing or moving the mouse, after the connection starts working again its like a huge lag because after that 15 seconds, everything that i typed shows up or the cursor will spazz out from me moving the mouse. this does sound really confusing and its reeeaaaaalllllyyyyy hard to explain, also the bluetooth icon in the top right corner has a dotted line through it. the "stop and lag" usually hasppends when im using an application and i click in the desktop area or i open up a new application when using an application. like i said this is really hard to explain so if anybody can understand what im trying to say, please help.