Frequent feeding - normal?

Sherbet Lemon

Until today, DD was eating once every three hours with a few "quicker" feedings at 2 hour intervals.  This afternoon, she's been eating at one to one and a half hour intervals... all afternoon long.  I'm getting exhausted, and my nipples are getting sore.  Is this a normal thing?  I'm hoping that all this eating now means that she'll sleep really well tonight and let me go 4 hours between feeding... but I'm worried if she'll let me get any sleep.  I'd love some input from those of you with more experience bfing.