.h5 file size is same before and after training?
This is not surpising.
h5 is the save file of the model's weights. The number of weights does not change before and after training (they are modified, though), therefore, your file should have the same size. 

To know if your model after training is better, you have to measure it : you have to make predictions on a test set, and measure it, with usual metrics like accuracy or F score and so on. look at this to see usual metrics used in machine learning.