There are several signs you can look out for to tell if your rabbit is sick or in pain. Some common indicators include:

1. Changes in behavior: If your rabbit is usually active and social but suddenly becomes lethargic or withdrawn, this could be a sign of illness or pain.

2. Loss of appetite: A decrease in your rabbit's appetite or a refusal to eat altogether can be a sign that your rabbit is not feeling well.

3. Changes in stool: Any changes in your rabbit's stool, such as a lack of stool, runny or watery stool, or abnormal color or consistency, can be an indication of illness.

4. Changes in grooming habits: If your rabbit has stopped grooming themselves or has a messy coat, this could be a sign that they are not feeling well.

5. Difficulty breathing: Wheezing or rapid breathing can be a sign of respiratory problems, which require immediate veterinary attention.

6. Changes in posture or movement: If your rabbit is hunched over or has difficulty moving around, this could be a sign of pain.

If you notice any of these signs or anything else that seems unusual or concerning, it is important to take your rabbit to a veterinarian as soon as possible.