"were" is the past tense of "are".
"was" is the past tense of "is".
"were" and "was" can both be used as past tense of "am" unless it follows "if" in which case only "were" should be used, unless the "if" in question asks for a person's age in which case it should be "was" as past tense of "am" and never "were."
This is the kind of nonsense that puts people off writing. Now I'm going to tell you a secret that all writers know that most people don't. There is no right and wrong when it comes to spelling and grammar, there are preferred spellings and preferred rules of grammar but it's never a case of being right or wrong.
Writing is an art. A writer's intention is to create a picture in the reader's mind about what is happening within the story taking place. The writer will often skip details that are deemed unimportant while going into precise detail about events relevant to the plot. The written word becomes a tool that coneys the story, not just telling the events but taking the reader upon a journey letting them see the events taking place.
There's no right or wrong way to paint a picture, and there's no right or wrong way to write a story. Of course once a writer has finished the story they will go through it with a fine tooth comb checking the grammar and spelling but it's just for the sake of making it an easier read.
Don't be too concerned about the structure of writing. Just get that story down. If someone tells you you're wrong for using the word "laid" instead of "lay", or tells you the word "agasp" doesn't exist just ignore them. You are the writer not them, write it your way.
Incidentally I'm a big fan of the Oxford comma.