First of all, like several people said, dump the "trainer." Dogs, puppies, kids, once someone tells you they are inherently bad, can't learn etc. you should be done with that (ignorant) person and never look back or question yourself for an instant!
You do NOT suck as a puppy mom. Those who do, do not seek training. They throw the puppy out in the back yard to languish and howl and cry until eventually the dog goes to the shelter. (I know, I rescued dozens with that kind of history.)
Five months old is a BABY. He needs lots of sleep, and _structured_ time for meals, crate training, potty training, other training, and vigorous play. Look up "Nothing in Life is Free" - with that he will learn that all good things come from YOU, to seek permission from you, and to follow your directions.
PLEASE don't let this "trainer" ruin your bond with your puppy. Find a kind puppy class, where you do the work directly with your puppy. He wants to learn that you are in charge; he will be much happier, and much safer.
FWIW, many long years ago, about 17, in fact, I took my first cocker, Feather, who was 6 months old at the time, to the dog training class at the local rec dept. First, the instructor said she couldn't be there without a choke chain on her, I said, "OK, give me my money back" and she relented. Then during the class she insisted that we "treat" the puppies for compliance.
Now Feather was not at all food motivated (she already knew when and where her next meal would be!) and she took the cheese treat politely, laid it on the floor, and moved away. The instructor berated me loudly in front of the whole class for bringing "a dog who was not hungry" and "the wrong treat!" I turned a deaf ear on her and praised my puppy.
I waited after class and the instructor rudely asked me, "why are you still here?" And ever so politely, I said, "I'm waiting for you to give me my check back. We won't be coming any more."
I was VERY CLEAR: no choke chain on MY puppy and only praise for what she did well = respectful training. I believe every dog deserves it, and every person has a right to learn to provide it.
Please, find a new "trainer."
Cricket, home 1-29-2012 - 3-29-2017, 5 yrs, 2 mo of Love
Sophie, 10-22-2015, home 9/19/15-
Maggie Mae: home 9/1/2014 - 3/31/2015, 7 mo of Love
Feather: 3/23/1994 - 11/17/2011, 17 yrs, 8 mo of Love