Tricky isn't it? They're starting to understand everything but can't talk to be understood themselves. I often think it must be like us going to a foreign country and really needing something but no-one can understand you.

My strategy is
a) are they hungry? feed them
b) are they tired? put to bed or do something else like sit down & read together
c) can I distract with something else until the overwhelming feeling they're experiencing is over?
d) try humour - this nearly always works, like peekaboo or surprise them with my actions (e.g. hide & seek)
e) hand over to DH if he's around as i give up & go & have a cuppa!!!

It could be teeth though - molars do take a while to come through and they really really cause issues for my girls for a little while (lots more than a couple of days).