Thank you for your question.
I'm sorry you are having trouble with your periods. I understand how worrying it is not to have it regularly and how awful it is to be in pain.
You didn't say if you are sexually active so I'm assuming that you are not pregnant. If you are then first please do a pregnancy test and see a gynaecologist.
If you're not sexually active periods can become irregular if the ovary does not release eggs regularly. This often requires a detailed history by your gynaecologist and blood tests to determine any hormonal causes. Irregular periods are very common in the first few years after they first start. Recently, a high fat high sugar diet, obesity, lack of exercise etc are causing more and more girls to have irregular periods. when they correct these their periods often return to normal and also become less painful.
Your gynaecologist can suggest medication to take during your periods to ease the pain. there is no harm in taking it as prescribed and it does not affect long term fertility.
so please do see your gynaecologist for the correct tests and treatment for irregular and painful periods.