Cluster feeding at 5 months

My lo is exclusively breastfed and has, over the last month or so, fallen into a pattern of waking twice in the night to feed. Suddenly tonight she has woken every 45-90 minutes since I first put her down at 8. Nothing soothes her, I've given her calpol as I thought it might be a teething issue, I've tried cuddles and rocking her back to sleep...only boob will do. 
Does anyone have any experience of this? I'm basically hoping for some reassurance that this doesn't last...exhausted isn't the word.