Someone’s texting a lot
Don’t ignore the signs. Does he usually explain after responding to a text, “Oh, that was so and so”? Well what about the times when he doesn’t say a word? Does he become quiet after certain texts that seem to require a good few minutes to respond to? You may want to ask one day (even though it’s nosey) “Who was that?” and see what he says. Chances are, he might already be on the hunt for (and in contact with) other women.