Is my phone malfunctioning?

Whenever I get a text a random number shows up in the text like the phone is counting down. I have no idea what is going on. I get the text but then a number shows up like [Text Message and the number 18 shows up] [Text message and then the number 17] it is freaking me out a bit, does anyone have any idea what this could mean, my phone has never done this before. Please help.