Help with vet bills for scheiss

I'm trying to raise money to help cover the cost of vet bills for my cat. He means the world to me. I love him with all my heart. Last night I took him to the ER because he was having trouble breathing and was in distress. They did as many tests as they could to fit in the budget of $500 because that's all I had to my name. I gave them everything I had. They told me he may have a heart disease that could lead to heart failure it not treated as soon as possible. But I can't afford the testing for any of it. I have never reached out to the public before but I need help, I'm only 20, I'm a care giver and don't make a lot of money, I spent all I saved up on my cat. I'd do anything to save him, he is my world. I can't afford his vet bills, but I will never give up on him. I rescued him from abusive people when he was just a kitten and promised him I'd always take care of him. He is the most loving playful cat I've ever met and puts a smile on everyone's face. He deserves the best medical care. I just need help from you. Anything helps. I can't lose my baby.