My boyfriend has been ill for half a month, and he doesn't answer the phone or return messages.

If your boyfriend is ill and doesn't return your phone calls and messages, then he may be experiencing some difficulties or need some rest and recovery. In this case, you can try to give him some time and space to recover.

While waiting, you can consider sending him a short greeting message to express your concern and support. For example, "I hope you can get well soon. Please let me know if you need help. "

But if your boyfriend doesn't reply to your message or refuses to communicate with you for a long time, then you may need to consider whether to wait or communicate with him further.