Why do i feel weak the morning after having sex.I ve once complain to a dr, he told me to rest after having sex that i should not get up immediately after sex. But now i notice that even if i have sex at night and remain on the bed till the morning after, i will still be very weak the next day. I do not think i have any heart problem cause i do go for regular medical checkup (bp, blood sugar, bmi, ear and eye). This feeling have been having close to two years. Am 35yrs Male