Why is LTE on my IPhone 5 so slow?

I got a new IPhone 5 when it came out and everything was working good but now my LTE is VERY slow… When I use the Internet, it doesn't even load up the webpage. I go home and use my Wi-Fi and its all fine (really quick actually) and I change my settings to turn off LTE so it's 4g I think and it goes much faster also. I thought that maybe I should leave LTE off and stick with 4g but when I have 4g I get very low bars.
I also looked this up on the Internet and some ppl had an LTE problem and it was wrong with an antenna or something and they had to replace their phone. I want to know if maybe I changed a setting off or something or if I need to replace something on my phone.

Most wirless company's LTE coverage is NOT very good currently, most of the major LTE providers are still upgrading and installing more LTE towers. This is almost certainly why your LTE is slow, its just not very good in your area.

Depends on your carrier and area.

I'm having the same issues. I don't think it's a carrier/area thing as it was working fine for the last few months in the same area. I'm thinking that a software update might be needed. So many things could cause the slowness, I'm just gonna go to the Genius Bar if it continues.

I used to have very good reception, but now is it sucks. I called my provider and they said is the phone issue. And I went to the apple store to verify if was true, but they said its the provider… I think so I'm going to quite.

I've had the same problem. I used to get awesome speed. Now it'll say that I have 4 or 5 bars of LTE and not even be able to open up applications that use internet. I'm honestly getting really fed up with it.