pkay i have PUPPS and its a rash that lots of pregnant women get
it sucks
best thing i can tell you is call your dr for it
if it is PUPPS (i hope its not because seriously im miserable because of mine

)
the they can give you steroid creme for it
until then go buy some hydrocortizone creme and some calamine lotion to help stop the itch
however it could also be dry skin
your belly streatches alot during pregnancy causing your skin to dry out