Internet connection keeps slowing down?

[Peter]

Sometimes when im using my Wi-fi it becomes really slow and has the yellow triangle pop up or it disconnects my laptop altogether. I keep turning off the modem and the router and waiting for upto 2 minutes before turning it back on, it fixes the problem but after sometime it goes back to being really slow. Also, places in my house that had very strong signal strength started to become weak. I was wondering if the problem would be fixed if I did a hard reset on the router? or do you think I would need to buy a new router or modem? Its a linksys router.