A hot pack on the tummy - like a wheat bag - will help the pain, lots of water, and I would try isolating what is causing it. Coffee and dairy did it for me while pregnant, and avoid those foods.
Short term, not sure there is anything you can take, panadol won't help a tummy ache at all, will probably just make it worse. Not sure if you can take Tumms while pregnant? Maybe call Nurse On Call and ask. Failing that, the best natural remedy for diarrohea is strawberry juice.
Sipping peppermint tea will help too with the pain. xxx