yes, i mentioned assertiveness in my previous post, and i definitely think the OP could benefit from developing more skills in that area.
assertiveness is not the same as aggression. it is like the midpoint between passive communication and aggressive communication, a healthy balance that helps us express our needs without being rude or mean.
there is also a great book that discusses both assertive communication and specific ways of communicating one can use to be more assertive. here is a link, the book is old, but it's a classic for these issues, and since it's old you can probably find a used copy for very cheap:
Amazon.com: When I Say No, I Feel Guilty (9780553263909): Manuel J. Smith: Books