Could Headaches And Nausea Be Related To Low IGM Levels?

I have had recurrent sinus infections for seven months. I also have severe headaches and nausea every day now. When blood work was first done in Jan. my igM level was 27 with normal levels of igG and igA. This week the igM has dropped to 21, with the other two remaining in normal range. I am 68 years old. I am very worried because I am not getting any better after taking many different antibiotics. Are the headaches and nausea associated with the low igM levels?