i find if i have too much caffeine during the day, i will wake at 2,3 or 4 am and not be able to get back to sleep either. too much caffeine is a relative thing but i am of similar age to you and live in a similar climate. similar exercise patterns too. i do have kids, a job and men and all those sorts of stressful things so lots to think about when i cant get back to sleep. for me, too much caffeine is over 4 decent sized cups of proper coffee a day. when i am being disciplined, i go for one with breakfast, one mid morning or lunch. one after school and then that is it. if i cut it down to 2 a day which i find really hard, i am feeling like falling asleep by 8pm and i sleep literally all night.