A nutritionist or hormone specialist could help with your diet and adding supplements to help regulate your period. Your OBGYN could talk to you about different ways to measure your hormone levels- specifically balancing progesterone and estrogen. Spotting is an indication you might get your period early. Longer times between periods is something I have not yet experienced, but regular cycle depends on how you maintain your diet, exercise and stress levels. There are all sorts of useful tools that can help with tracking your diet and cycle to report to your obgyn. Food journals, medical specialists, apps for dieting and feminine health. On the what week is spotting likely? For different women this may happen at different times of the month. Best way to avoid this, in my personal opinion, is to keep your diet consistent and if you take meds or supplements, be sure to take them at close to the same time of day. Sensible dieting in addition to supplements such as ashwagandha at night to help me sleep, rose hips every morning, and a basic women’s multivitamin have helped me determine my cycle. Also, higher levels of folic and amino acids, potassium, magnesium, zinc and vitamin C are good.