Congratulations on hooking several projects. That is a sign that you are offering something that is in demand. As @eschutte2 suggests, lighten your workload.

Congratulations on hooking several projects. That is a sign that you are offering something that is in demand. As @eschutte2 suggests, lighten your workload. Offload some of the work to maintain your health and sanity. Finish the current client's work. Then revisit the other clients and ask for more money. It's the old supply and demand balance. If there is that much demand, then you should be able to raise your rates.