This details the combination of metronidazole and quinacrine for chronic giardia.
I know you're hesitant to take meds but it really is the only way to finally get rid of you problem. The key is making sure you take the correct protocol.
As you can see in the paper, the protocol is a combined metronidazole, 750 mg, 3 times a day for two weeks and quinacrine, 100 mg, 3 times a day for two weeks.
As mentioned, quinacrine must be picked up from a compounded pharmacy.
You probably will feel shitty during this protocol. Like my EH, these bad boys need to die off inside of you and will make things very uncomfortable. Drink A LOT of water while taking the meds and make sure to finish the course. You may not feel better immediately but give it a minimum of 4-6 months before reassessing.