My 18mnth old runin fever of 102.8 not breakin wit meds but she been acting fine for the most part all day like this what should I do.?

Other infections. Most high fevers in toddlers are due to viruses. There are as many different types of viruses as there are types of trees. This time of year could be adenovirus, parvovirus, roseola.....The list goes on. If she is not too sick, it is less likely some other bacteria has got hold of her - things like a blood infection, urinary tract infection, pneumonia. Keep watching child closely and push fluids!