6 Weeks - Longer sleeps, shorter feeds

My baby will be 6 weeks tomorrow and is exclusively breastfed. The past two nights she has had longer night stretches (one was 5 hours) and her nursing sessions have been shorter. 5-10 minutes sometimes, usually every 2 hours. She has always been a quick nurser, but the sudden change has this first time momma overanalyzing. She has plenty of wet and dirty diapers. Anyone else experience this? I'm taking her in to see her pediatrician tomorrow, but I think her weight has been steadily increasing.