Is it unusual to get 5 when a pair of dice is rolled?

Not at all. In fact, there are 4 ways to roll it:

A 1 and a 4 or a 4 and a 1

A 2 and a 3 or a 3 and a 2

There are 36 possible ways you can roll 2 dice, so those 4 possibilities represent a 4/36 = 1/9 chance of rolling a total of 5 between two dice.