Should a babysitter get paid when the person she babysits for takes vacation time?

I babysit a 15 month old baby. I watch him 3/12 days a week for $75 (which just started recently..before it was $50).  I never get told in advance if dates or times change. I am assuming this is because our husbands are friends. I just missed a week because of a surgery which was understandable.  Now it seems I hear a vacation is comin up where I will not work for 1 week and a half.  Times are tough and I need this money.  Other people have told me I should get paid whether or not.  What do you think?