What Causes Extreme Migraine Headaches After A Spinal Surgery?

I just had my l5s1and l45 fused 3 weeks ago I m now having extreme migraine headaches everyday I wake up to them and go to sleep with them my spinal cord was leaking fluid but they said it was fixed these headaches have been going on for almost 2 weeks now I m desperate for any kind of answers please help me no medicines are working I m scared