Welcome to HCM.
Bleeding before period is most likely due to some hormonal
,fatigue,weakness may occur during bleeding.
Heaviness and pelvic pressure is usually due to Uterine cramps
Sometime early or late period might be due to stress,anxiety,work overload,diet and other underlying disease.
Take oral NSAID with dicyclomin to subside pain,cramps.
Start haemitinics,b12 and calcium supplement
Go for certain investigations under guidance of doctor to rule out any condition.