The dosage for different drugs is really not comparable. It depends entirely on how the drug reacts in a person's body. I wouldn't worry about "100 mg" being a big number or anything like that if that's what is bothering you. From what I've seen on here, 10 mg of Lexapro is a normal dose, but 150 mg of Wellbutrin is a normal dose... compared to 1000 mg of Tylenol for a normal dose
If you're reluctant, talk to your doctor about staying on 50 mg for a while longer to see how you feel. But if 50 mg isn't having any bad side effects that's a good sign that 100mg might not either.
Basically what I've learned from talking to people is that some ADs will give you bad side effects, but that doesn't mean anything about the next AD you might try. It might be perfect with no side effects.