hi Beams,
well done for getting back to exercise.
Headaches after exercise are not uncommon, and in most instances will go away after 1 or 2 weeks, but do contact your gp if they persevere any longer.
The main reasons why people get headaches after exercise are:
1. DEHYDRATION: as mentioned above the human body needs plenty of water to survive and if you exercise you need to up your intake of water. A headache can easily be a reaction of your body to the lack of fluid.
2. LONG PERIODS OF GOING WITHOUT FOOD: if you exercise first thing in the morning and the last time you ate was the previous night, it is possible to get a headache due to the drop in sugar levels.
3. HIGH INTENSITY EXERCISE: if your workout is quite strenuous and you are quite new to it, it is possible to get headaches as all the blood vessels in your head dilate in order to keep up with all the work your heart is doing, and this results in a headache.
All of the reasons above should improve within 2 weeks since you started your training…but if it doesnt go and visit your gp.