My 5 year old Male Bulldog has been losing weight over the past month or so. I have switched his food and have increased portions. I have tried feeding him rice and boiled chicken. His appetite has never been great, but he has always maintained a healthy weight until lately. He has been eating at least once per day, often twice. I started putting hot water on his food, mushing it up, letting it cool and then giving it to him. I have also started feeding him from a raised surface. He is definitely underweight though and even appears to be losing some of his muscle tone. Any ideas on what this could be caused from or how I can help him to gain weight??