Diversify your income stream, never rely on a business that you can NOT control by yourself. If you want to quit your job, I suggest you to do something that is related to your current job, don’t waste your resource or knowledge and experiences from that job.
You are providing photo edit service, that’s a good start point because you could accumulate clients, they always need your service, so I’m in your shoes, I’ll try to convert a customer to be my loyal clients, not only on Fiverr but on my own website. I’ll build a website, and develop a subscription package, that would make your income more stable.
Another suggestion is develop more needs from your customer. Except the photo editing, do you know any other services they need? If you find some, then try to create a other gig, or find someone could able to do that for you.
When you are too busy to handle orders, try to learn outsourcing low level tasks, to move your income to the the next level.