Hi Floss,
Like the other ladies who have responded I too had that sort of discomfort through the early stages of my pregnancy ( I am now at the end of my 33rd week). Mine definitely came from the side my bubba egg came out of...which was confirmed by my ultrasonographer (is that what they are called?). It's pretty amazing what these people can see inside. I also had a very painful period after I conceived, with ridiculous back pain but all was well with my little bubba as my 8 week scan showed.
Unfortunately it is certainly a topic in books that really isn't described / covered well and it has only been through talking to other pregnant women that I know it is a very normal feeling to have. When in doubt though always contact a health professional....
All the best with the pregnancy...
Bianca