hi L.,
my daughter is 13,5 months old, she's been doing all-of -the sudden screaming for few months without any signs of teeth at all. i don't know what it is either, maybe teeth , maybe night terrors( which i heard are more common towards 2nd yr)also could be separation anxiety (baby feels that he's alone, just wants to be reassured you're near by) my daughter does this screaming most of the time in the 1st 2-3 hrs after i put her to bed. i don't think you gonna know for sure, only he knows, but could be any of these reasons or more. just wanted to let you know you're not alone. my ped told me it would pass eventually like everything else with babies.