I Have Been Taking Octagam For 3 1/2 Years One

I have been taking Octagam for 3 1/2 years one time a monthly , my levels have been steady until the last 5 months or so . The physician increased the dosage to a 45 , and my levels continue to drop last week my level was around 500 I am very sick for about 3 days after each Infusion with flu like symptoms. What is causing this and what is going to happen to me? I feel so bad sometimes I feel like I am dying. Any feed back would help. Thanks
Nancy