Hi Jenny,
I don't have access to the OPR's but I have the Bitish Vital Records CD's and have found quite a few children who I'm presuming were born to your couple.
It seems that Robert's wife was Eupham and not Euphemia as you had thought.
Anyway, here they are:
John MCCULLOCH, Born: 24 Apr 1745
Birthplace: Linlithgow, West Lothian, Scotland
Recorded in: Linlithgow, West Lothian, Scotland
Father: Robert MCCULLOCH
Mother: Eupham GILLIES
James MCCULLOCH, Born: 12 Nov 1747
Birthplace: Linlithgow, West Lothian, Scotland
Recorded in: Linlithgow, West Lothian, Scotland
Father: Robert MCCULLOCH
Mother: Youpham GILLIES
Agnes MCCULLOCH, Born: 7 Jul 1750
Birthplace: Linlithgow, West Lothian, Scotland
Recorded in: Linlithgow, West Lothian, Scotland
Father: Robert MCCULLOCH
Mother: Eupham GILLIES
Robert MCCULLOCH, Born: 3 Aug 1755
Birthplace: Linlithgow, West Lothian, Scotland
Recorded in: Linlithgow, West Lothian, Scotland
Father: Robert MCCULLOCH
Mother: Eupham GILLIES
William MCCULLOCH, Born: 3 Aug 1755
Birthplace: Linlithgow, West Lothian, Scotland
Recorded in: Linlithgow, West Lothian, Scotland
Father: Robert MCCULLOCH
Mother: Eupham GILLIES
Susanna MCCULLOCH, Born: 26 Sep 1757
Birthplace: Linlithgow, West Lothian, Scotland
Recorded in: Linlithgow, West Lothian, Scotland
Father: Robert MCCULLOCH
Mother: Euphan GILLIES
Hope this helps,
Anne