I need suggestions on what to include in my reconsideration letter for an apartment...

I was recently sent a rejection letter from an apartment complex due to rental history. Apparently the last 3 years I rented with a guy doesn’t count due to the fact that it wasn’t listed as an apartment with the town. The woman told me if I wanted her to reconsider, write them a letter. I was planning on just letting this apartment go but unfortunately I have only 3 months before the baby is born and we desperately need a 2 bedroom that we can afford. So what exactly should I say in this letter? Usually I’m good with words but under pressure I get writer’s block! Any suggestions would be appreciated.