for he has been longing for you all and has been distressed because you heard that he was ill. (Philippians 2:26, ESV)Epaphroditus is also wanting to go back to Philippi, it isn't simply that Paul wants to send him, he also wants to go. And his two-fold reasoning is fascinating.
First, he is simply longing for them. He misses them and wants to ... genuinely wants to... be near them. Secondly, he is distressed, but not for his own sake. It has been eating him up because the news of this illness that Epaphroditus must have suffered has made its way back to the Philippian Church. So, he knows... that they know... that he was sick! But it isn't his illness that is distressing him, it is because he knows that they have been worried about him.