If you had some success with your original treatment, then it could be that you didn't continue with that protocol for long enough. I don't think with any infection or parasite, 30 days only has helped anyone ever.
Your second round of treatment sounds good. If you do have giardia, you might add tumeric to your new regimen, and eat as much raw garlic as you can tolerate.
Colonics can also be helpful, as well as enemas to keep the flow of toxins going out. The raw garlic will not only help with the infection, but it help with your gut flora also, as I have been reading about, and experienced it on my own, which makes me believe it might be true.