I'm 35, Recently Returned From An 18 Day Trip To

I'm 35, recently returned from an 18 day trip to Costa Rica and Bocas Del Toro, where I regrettfully drank the water. Since my return 6 days ago I have been experiencing flu like symptoms from about 12:00 to 5-6:00 pm. I'll feel fine in the morning but then start feeling a headache in the back of my head along with neck stiffness, loss of appetite, ears clogging, and sometimes ringing in my ears. I'm wondering if I've contracted a viral or bacterial infection, if it's returning and climate related, or if it migraine related. Thanks.