It's not bad, it's normal. I personally think it's great that you can be so in tune with your body you notice them early! Can't remember when I first noticed my BHs, but I'm fairly sure it was at the end of the 2nd trimester. 7th of October, according to my pregnancy diary, so I would have been... 23w.

ETA: I'd been over-doing things that day too, and the baby didn't come early - as you can see! I first noticed the colostrum the day after that so keep your eyes open!