BeaWheesht I can totally understand how you feel. I have 3 young children and become extremely anxious whenever they are ill. I always think that any illness is going to be life threatening, and also panic about cross contamination to the others. I too am on sertraline.
can you give her some calpol to alleviate the pain ? Is the pain coming and going, like gut spasms ? Does it come before a poo ? This can be normal for a tummy bug.
Don't worry unless there is blood in her poo, and even then this can be normal, but if there is, the GP will probably want to take a specimen. ( my son had lots of blood in his poo, and he turned out to totally fine )
Have you checked her temperature ? Again, can be normal with a tummy bug, but if you treat it with calpol/ibuprofen, it may make her feel better.
Keep her hydrated, and if possible, get some dioralyte into her. In my experience, they don't like the taste, so I give it in small amounts often from a syringe. Also you can get fluids in via ice lollies.
I am here for hand holding....not going to bed for ages.