My iphone 5 is sometimes slow and sometimes fast?

My iphone 5 is sometimes slow and sometimes fast?
sometimes when i'm using LTE on my iphone 5, my iphone 5 would slow down all of the sudden but then when i turn it off for a day its really fast. This happened at my house where i have been using my iphone for a long time and its fast there. This issue happens alot, its not my first time for this. I seriously need help
is there something wrong with my iphone? Is there like a virus? I'm scared.

IPhone sucks