Messed up migrations

Hi, 

I was creating my application  little by little, adding classes and making migrations.

I had an error in on of the migrations and it didn't create de tables. I deleted the migration but now when I try to create a new migration, the classes that were on the deleted migration are not on the new migrations.

How can I solve this problem? Is there a way to reset the migrations so it read the classes again and make needed changes on the database? 

Thanks in advance.