I had the same thing for ca 3 months from around 13 weeks. Bizarrely, it was not the tummy that itched as one would expect but my back (esp around the spine), shoulders and legs.
I did liver bloods to exclude obstetric choleostasis, and they came back fine, so it must have been some funny reaction to the hormonal upheaval (ok, it was not that funny at the time, when my back looked as if three angry cats had landed on it... Not only was it uncomfortable, it was socially awkward when I had an urge to scratch every ten minutes in the middle of a meeting.)
No amount of lotions and potions helped, and I tried loads from Clarins oils to aquaceous cream; my skin felt lovely and smooth - and itched like crazy. I was prescribed an anti-histamine which made it marginally better for half a day but one pill knocked me down and I felt groggy and unwell for 48 hours so I gave up on it. In the end the only thing that gave some temporary relief was dry brushing. I would get up in the middle of the night to use one of these long-handled bristly brushes - ah bliss!
I suggest you have you liver function tested to ensure you do not have any issues there, but otherwise, alas, cannot recommend any miracle cure. But this will pass!
Wishing you an easy rest of the pregnancy and a healthy baby.
x