Change the AutoCorrect so that it doesn't include a line skip.
Go to Tools > Autocorrect and enter whatever it is that you have set to be
autocorrected in the Replace box. The list below will scroll and select the
autocorrect (it will probably show with an asterisk at the end). Click on
Delete and it wil be deleted from the list but will appear above it and
show as formatted. Click the plain text radio button, edit the asterisk out
and press Add.