Why does my nipples get sore when my period is coming?

Hormones. This is something that a lot of girls find happens to them. Before your period, your breasts can get sensitive or even sore, you can get cranky and moody, you may put on a couple of pounds, and you may have a craving for chocolate, or just food in general.

Not everyone gets all of those things, but they are all normal. The good news is that most of them go away as soon as you period starts.

So what do you think about my other question about me having a period every four months

I didn't see that one. Once every four months doesn't sound round. Might be worth talking to your doctor, checking that everything is working properly. What age are you?