Cat Connundrum

I've been caring for a sick cat these past few weeks. It started out with Charlie licking and pulling his fur from his belly and many of his paws. When I brought him into the vet, he noticed a sore on the back of his throat. The vet gave me some food to see if Charlie had a food allergy and an antibiotic for the sore.
Well, after three days, the antibiotic made him sick and he wasn't really eating the food.
Now, he's been drinking a ton of water and hasn't been eating very well. As of post time I'm still waiting on blood work from the vet and am just wondering what will happen.
I keep reading online about different possibilities. I watch every move he makes and ask whether it is unusual for him or is cause for concern. Honestly, I'm acting a bit crazy.
I am by nature, a worrier. I always think there is something I should be doing and worry about the how things will go in the future. I wonder if he's on medication how I can go out of town?
Who will look after him? Am I not giving him enough attention?
As I said, it's a bit ridiculous.
But what I can do? Waiting is hard. Charlie isn't very clear about what's bothering him. So I feel like I should try and decode anything I can decode.
How am I going to survive having children if a sick cat gets me this worked up?
These are all good questions. Fortunately, I have great friends who help me work some of this issues out. I have a wonderful girlfriend who listens to me worry all the time and amazingly, doesn't get sick of hearing it. Charlie is a great companion and a very loving, gentle cat. I'd be torn up if something serious happened to him. But, the worst thing is not knowing. It's feeling like I should be doing something differently or something better. Could I? It's possible, but I doubt it. I just have to use my instincts and stay in contact with my vet. I also have to accept that the vet is doing his own guesswork.
Most importantly, perhaps, is that I just have to appreciate the time I have with Charlie. He's wonderful and loyal, and I do love him dearly. I just want to do so for a lot more years.