I Have 3 Kids A 6yr Old 2 Yr Old

I have 3 kids a 6yr old 2 yr old and a 8mnth old..
My eldest child is having abdominal pain+vomiting somtimes..
N even loose motion 2-3times a day..
And my othr kids too dnt seems well..
Dey dnt hav any symptms bt they are nt eating anything as if they too hav stomach upset ..
Evn i am feeling the same now..
Its nt dat severe bt still i was nt able to send hr to school..wat can i try before consulting the doctr?
Is it contageous?