I would take a guess and say you need a new string the bow is 2 years old and if it is still the original string I would replace it.

I use and recommend strings from gibblet here on the forum he makes some of the best string I have used and over the years I have used a lot of different strings.

Not only are his strings top quality they are also very affordable for the quality he could really charge a lot more for them and get it but he is just one of the guys who like to look after his customers.