The last couple weeks I've developed a headache during training sessions. The first time it came on very sudden during the tail end of a set of heavy breathing squats. It felt like my brain was pushing out of my skull. The headache didn't fade until the following day and so I backed off the intensity for the next few workouts but noticed as soon as I push hard with working sets it returns with a vengeance. Unlike the first occurence it fades a couple hours after a workout. I've trained on and off for 15 years and never had headaches from training before now. Is it something that typically goes away in time and anyone else experience this?