I am 17 years old and I am having a problem with...

The normal menstrual cycle is about 28 days plus or minus 7 days, so the normal menstrual cycle is about every 21 to 35 days .

Treatment of the menstrual irregularity and delay :

The treatment is being decided according to the cause of your symptoms after doing investigations and medical examination and determining  the cause and the diagnosis and treatment are detected by the doctor .
The treatment in case of polycystic ovary includes hormonal therapy like OCP .
In case of thyroid distinction the treatment includes thyroid hormone replacement .
In addition, you have to avoid stress, being worried, emotional stress, being exhausted and you have to eat healthy food and drinking plenty of fluids .

Diagnosis of the menstrual irregularity :

The diagnosis is made by taking full history and clinical examination of the patient and doing investigations including blood investigations like CBC, inflammatory and infection marks ESR and CRP, pregnancy test, thyroid functions , ovarian functions , estrogen , progesterone and testosterone levels and doing pelvic and abdominal ultrasound .

Causes of the menstrual irregularity  :

- Polycystic ovary
- thyroid disfunction
- pregnancy test 
- stress
- severe exhaustion 
- Obesity 
- loss of weight 
- emothional stress

Advice :
See the doctor .