Premenstrual syndrome (PMS) can strike like clockwork every month: Backaches, headaches, bloating, fatigue, irritability and anxiety are all signs that your period is on the way.

Dr Kelly Loi, an obstetrician and gynaecologist from the Health & Fertility Centre For Women, says PMS symptoms are cyclical. “They follow a definite pattern, occurring before the menstrual period and getting better once the period starts,” she says.

She suggests keeping a “menstrual diary” and reviewing it regularly with your gynaecologist to track the symptoms and understand your cycle better. You can record your symptoms, your mood before, during and after your period, the duration of your bleeding, whether the bleeding is heavy, and so on.

The causes of PMS are unclear but Dr Loi says it is related to the hormonal changes that occur before your period. These changes affect each woman differently, so some experience more severe symptoms. If you’re prone to stress and depression, it may make your PMS worse.

After giving birth, some women report that they no longer experience PMS symptoms, but for others, it actually becomes worse. This is also believed to be due to hormonal changes, says Dr Shiv Gill, a general practitioner from My Health Partners Medical Clinic.

If your symptoms last weeks or months at a stretch, and there is no obvious pattern to them, then you should get them checked out.

Dr Seng Shay Way, a consultant obstetrician and gynaecologist, as well as reproductive endocrinologist from KM Seng’s OG Practice at Gleneagles Medical Centre, says you should consult a doctor even if your symptoms follow a pattern, but are severe and affect your quality of life – for example, they prevent you from working or carrying out your normal activities.

Here’s a look at when it could be something other than PMS:

Irritability and mood swings 
These may point to a hormonal imbalance or thyroid disorder. “If your mood swings are associated with abnormal bleeding – such as in the middle of your cycle – the problem is likely to be hormonal and should be investigated,” explains Dr Gill.

Anxiety and depression
These too might be due to hormonal imbalance, or just extreme stress from a job or personal issue. Says Dr Gill: “If you’re having personal problems and your period is more than two weeks away, that could explain why you’re feeling blue. But if not, see your doctor because it could be your hormones.”

Breast tenderness 
Swollen breasts before your period usually indicate PMS, says Dr Gill. But if tenderness persists after your period, or there is nipple discharge, ask for a breast ultrasound or mammogram to rule out cysts.

The hormone progesterone is a culprit in menstrual headaches and migraines. But that throbbing head might also be caused by not drinking enough water, being under stress or lacking sleep.

This is when you should see a doctor for a headache: The pain hits you right after you’ve woken up but improves as the day wears on. “The most worrying headache is the persistent, early-morning kind that gets better throughout the day,” says Dr Gill. “It might be a brain tumour, as a headache is an indication of pressure on the brain. As the day goes on, that pressure is lifted and you don’t feel it anymore.”

This sort of headache is easy to ignore but if you experience it, and especially if it comes with nausea or vomiting, you must see a doctor.

Bloating and abdominal pain 
If it lasts for several weeks, it might be a sign of something more serious, such as ovarian cancer, says Dr Gill. “The symptoms of ovarian cancer are very vague, and don’t show up until the disease is at an advanced stage,” Dr Gill explains. “So if you constantly experience bloating and abdominal pain, don’t put it down to overeating, constipation or PMS. See a doctor right away – she will give you an ultrasound scan to rule out ovarian cancer.”

Back pain 
Chronic lower back pain may indicate fibroids, non-cancerous growths that develop inside or outside the womb. The back pain may come with heavy vaginal bleeding, pelvic pressure or bladder discomfort.

A persistent, stabbing lower-back pain might also be due to endometriosis, a condition where the endometrium or womb lining grows outside the womb.

PMS makes you feel more tired than usual, but if you experience this throughout the month, you may have an iron deficiency or anaemia – a simple blood test at your GP’s can confirm it. More serious causes of fatigue include diabetes, hormonal or electrolyte imbalances, thyroid problems and depression, says Dr Gill.

This article was originally published in Simply Her September 2013.