iphone 5 calling problems?????

i dont knw what is wrong with my iphone5 it started a week ago when i end a phone call a weird sound comes up for a second a sound like it lost connection and yesterday it got worse i tried calling and i ended up hearing my own voice an echo and the other person im calling is hearing wierd noises like losing connection (kheshhhhhkeh) and im sure nothing happened to it im so carful with it and i have a cover on it i just bought it one and half month ago maybe what is wrong with it???? please help what do i need to do