Hello Loca! Thank you so much for visiting the website and for posting your question! I agree with alison b--I'd really feel a lot better if you'd go in and get your breasts and nipples checked out by your doctor. Would you mind sharing your age and also when your last mammogram was? It might be time for another one, just to rule out anything potentially troublesome.
Like alison b said, since they come and go it may be nothing to worry about, for example, did the odd bumps happen to start around the same time you got a new bra, or changed laundry detergents, or did anything else different around your breasts? About how long has this been going on? If you are able to think back to when the bumps started appearing, you might be able to pinpoint an environmental cause.
Either way though, it would be a good idea to check them out with your doctor. For me, when it comes to our breasts, we just can't be too careful. Please post again and let us know what you find out.