A boy sent a message saying that I was ill, very ill. What does he want to express?

What this boy means is that he misses someone very much now. When he said he was ill, he meant that he was lovesick, and it was very serious, which showed that she missed another person very much now. As for who this person is, only this person knows.

Another possibility is that when she quarreled with others, others said that he was ill, and he deliberately sent this sentence to the other party. In other words, now two people have begun to get angry, and both of them are unwilling to accept each other and wait for each other to bow their heads, but in fact this is impossible, and feelings need to be compromised and compromised. If two people are unwilling to compromise for each other, then such feelings will soon end.