Yes - you have to start of slowly or you will sometimes have some serious reaction. Some people get diarrhea - so it is always best to start slowly.
Drops under the tongue is usually what is recommended until you can tolerate more. And - you will have less chance to have negative reactions or at least less severe reactions.
What you were going through is called a healing crisis and that is when your body is getting rid of years of alopathic medicimes in your system as well as your diseases.
If you start slow - you will be better off.
I would try only a few drops at first for the first few weeks and gradually build up my intake.