Intermittent Toothache

I have toothache that comes and goes.
Is there dental experts who can explain why or how exactly it should be itermittent?
"I get rid of the pain by taking painkillers may codamol 500mg twice daily.

It is very difficult to answer the question without more information.
1. The tooth / area of your mouth? Does the tooth have a filling in it? If yes, what type of filling (metal or composite)?
2. What is your age?
3. What type of pain is a dull ache or sharp pain?
4. What do you mean by "coming and going? to know how many times have you pain (daily, weekly, monthly) and how long does it last (probably difficult to answer if you use analgesics)

My daughter has had this problem with a tooth that had been filled. She was in considerable pain on and off for a year. The dentist said it was because she was grinding his teeth in his sleep. (Which, as it is not accurate.) She was in so much pain when she was on holiday in Spain she went to the dentist who took Spanish radiography. X-rays showed that the filling has been pressing the nerve and there was an infection at the root of the tooth. The dentist removed the filling and permit the tooth to drain. The tooth was re-filled after about 14 days. No problems since.

I get this if im grinding teeth in my sleep. I have a loose tooth. just need to readjust and im fine the next day. sleeping with his mouth open (no pressure on your teeth)

It is a filling or cavity that is beginning to expose the root. You will need a root canal or the tooth removed or recycled.
If you are a dentist's chicken, make a paste with a solvent of some aspirins with water, put the right stick on the tooth and let it rest there. It will kill the root for good.

loose tooth, eroded enamel or gums, or it could be just what you eat or drink.
Whatever you need to see a dentist as soon as possible. Given all that codeine twice a day is not desirable.