I think you have a problem most people your age would love to have. That being said, I get it. It's easy to get burnt out - especially when you're trying to continue your education at the same time. If I were in your position, I would definitely look to my fellow classmates or any friends I had that would be a good fit. I'd probably bring on one more person (maybe two, depending on what they could help me with) and split everything evenly between the two of us. If the tool you've created is that popular, everyone working on it will be in a great position down the road. You'll either be able to turn it into a full-time business, or leverage the crap out of it when you go out looking for a full-time position elsewhere (companies will love hearing about it). Either way, you've been hit with a blessing - I wouldn't give up on it just because it got too popular for you to handle. That's a great thing. Congrats!