What type of flea drops did you use?
How much Benadryl did you give and how much does he weigh?
Was it plain Benadryl?
Pseudophedrine is not particularly safe to use in dogs without direct vet supervision so please don't give him more of that. You can read about this here
Unfortunately Seargents flea drops are extremely toxic and many dogs react badly to getting more than one dose of them over time.
This is just one of many sites discussing the bad side effects seen in some dogs
And you can see the letter about testing done by the EPA on reactions to this product here
This product for dogs contains cyphenothrin and some animals are sensitive to it.
You may want to wash your dog off in a mild dog shampoo that has no insecticides in it or you might try in a pinch Blue Dawn dish detergent or Murphy's Oils soap just rinse really really well no matter what you use.
Another suggestion is to keep the dog in a dim quiet room to help reduce stimulation.
If you want to use an antihistamine with a dog Benadryl is a typical one used.
You can read about it here
If your dog gets worse I'd consider seeing an emergency vet with him.
I do not think this is worms I think its the flea product you used.
Hope this helps you!