Why does my Wi-Fi come and go?

So I was simply using my iPhone 5 (I have T-Mobile 4G LTE) and then usually the 3 bars will always pop up. Then something happened that says "LTE" it was like that since yesterday and apparently I got no Wi-Fi. I disconnected and connected. I have 2 Wi-Fi names that work perfectly. One connects and disconnects itself. And the other one dosent connect at all. What do I do? Is their something I have to unplug and plug again so make it work again?

First try to reset your phone (Hold Sleep/Wake and Home buttons about 10 secs or more till Apple logo appears).

If that doesn't work go to Settings > General > Reset then choose Reset Network Settings option.

If one of these two options doesn't work, it may be a router issue. Try unplugging your wireless router for 30 seconds then plugging in again.

If the problem still persists, there should be a little reset button on the router (usually a little pin hole in the back where the plugs that you have to insert a paper clip into to hit the button). Press the router reset button while the router is plugged in and this restores the router to factory default settings.

I would be surprised if one of these steps doesn't solve your problem.

You need to be clear about what you are looking at. 4G LTE is NOT Wi-Fi. That is a cellular signal.

Wi-Fi is subject to a great deal of contention for bandwidth in the 2.4 ghz band where most people are. You are using it, your neighbors are probably using it, and other devices, such as baby monitors, microwave ovens, bluetooth devices and cordless phones, to name but a few of the devices which use it.

There are many thing syou can try. If your router supports it you can try increasing and decreasing power strength of the router (and yes, decreasing can help particularly in areas where you have a lot more contention with other signals. Reducing power reduces the overlap so that there isn't as much contention). You can also use reflective surfaces like aluminum foil to shield the connection from some directions while focusing/reflecting it in others.

If you decide that you need to upgrade for any reason, be certain that whatever devices you acquire support 802.11ac in addition to 802.11 b/g/n