Hello, my guinea pig is a 3 and a half year old male. He never had health issues. Today I noticed that his abdomen is pulsing like a heartbeat and I've never seen him doing that. He eats like he's always done, he eats hay and vegetables, he drinks, he moves and jumps and everything. He just has this weird movement which I can't figure out. Can you tell me what this is about or what can I do? I can't go to the vet today. Thank you.