Why do I have more discharge before my period?

Because in the days before your period your hormones shift from oestrogen to progesterone, and progesterone changes what your cervix produces: from thin and stretchy to thick, cloudy and white. For most women that change is a normal, expected part of the cycle, not your period starting early and not a sign that something is wrong.

The change follows the same pattern every month, which is what makes it easy to place.

• Around ovulation, discharge is thin, clear and stretchy. Oestrogen is dominant here, and it produces the wet, slippery mucus that fertility tracking relies on.
• After ovulation, progesterone takes over. Studies of cervical mucus across the cycle find it becomes thicker and more concentrated once progesterone rises, the reverse of the ovulatory pattern.
• In the days right before bleeding starts, that thicker discharge is usually what you notice. The NHS describes normal discharge as thin, clear or milky white, and ACOG notes it becomes noticeably thicker and heavier in the weeks leading up to a period, both as an ordinary effect of the monthly hormone shift. It often shows up in the same week as other premenstrual changes, like the exhaustion many women feel before their period, for a related hormonal reason, alongside the headaches some women get in the same window, the mood swings some notice in the same window, the breakouts driven by the same hormone shift, and the breast tenderness many notice in the same window. How many days into your cycle that week falls depends on how long your cycle runs; see what counts as a normal cycle length for the usual range.

None of this is your period starting. What actually counts as hayd is blood, with a specific colour, thickness and smell, not clear or white discharge, however much of it there is. It is also not the same thing as the white discharge that marks the end of a period: that sign is specific to discharge that follows bleeding once it has actually stopped, not to discharge that shows up before bleeding starts at all. If it is the bleeding itself that is irregular rather than the discharge around it, istihadah vs hayd is the relevant question, not this one.

What is worth a doctor's visit is a change from what is normal for you, not the discharge itself. Mayo Clinic and ACOG both point to the same warning signs: a thick, cottage-cheese texture with itching, a strong or fishy smell, a green, grey or frothy discharge, or discharge alongside pelvic pain or fever. Those usually mean a yeast infection, bacterial vaginosis or another common, treatable cause, which a clinician can identify properly rather than you guessing from a search.