My Eggs are Making my Head Hurt....

I took my AM dose of 225 IU of Gonal F this morning and my head was killing me all day. Why is it when there is a side effect to a medication, in this case 22% of Gonal F users get headaches, that I get the side effect? I know I cannot take Ibuprofen or aspirin so I have to wait until tomorrow, 2 more doses later, to see if I can take anything. :(