My cat which is male, 1 1/2 year old, is acting sickly. Meowing at times, and weak in the back end of body. Laying down and almost asleep. Very unusual for this cat. He is trying to tell me something is not right. He has gone off by himself and is just laying there. Ate well yesterday, but sure about today. He has food out at all times, so not sure how much he has eaten. Any idea?