I believe the fasting during Ramadan would actually help in getting rid of parasites by way of Humaworm. But, as incis said, the intake of plenty of water is crucial to flush out the toxins released by dying parasites. If you don't drink water during the day, die-off symptoms could be bad indeed, and you would suffer unnecessarily.
As you consider yourself as being sick, I would believe that you should be exempted from having to stick to all the rules concerning Ramadan. I cannot know about your particular circumstances, but any Imam with some senses left would allow you to drink all the water necessary to lessen your plight, and this by the grace of God. If you know somebody teaching the word of God, speak to him and try to get his absolution (hope this is the right word), so as that the water intake necessary during Humaworm treatment is a) officially allowed, and b) the thought of maybe braking the rules of Ramadan is not a burden to you anymore.