Ibuprophen 600mg

is it bad to take two for a headache??

cause I always do. but sometimes I feel like taking three...

take what is recommended.
there are health risk to any increased dose in all drugs.

I've heard jogging daily aids in alleviating headaches.

Yes.
A recommended dose is two 200mg tablets for 400mg of the med.
At one time I was taking 3-4 tablets several times a week, and it did bad things to my stomach.
Talk to your doctor - you must have one because ibuprofen at that strength is prescription.

400mg every 4hours is fine and I believe it's something like not more than 8 in 24hours. If you take 600mg you are unlikely to get any severe side effects unless you have other health issues like any organ failure, especially kidney problems. It will most likely just give you diaherrea and just make your symptoms worse, so it's really not worth it!
Also just so you know...paracetamol is much better for headaches, ibroprofen is better for swelling and muscle pain.
If you are often getting very bad headaches which get worse with light (in particular glaring sunlight) and noise, the pain is on one side of your head and/or in your eyebrows (although this isn't always the case) and often accompanied by nausea then you are most likely getting migranes and need to get prescribed meds. I find paramax works really well.
Hope this helps x