Read our lips. All the letter needs to say is "I disagree with this decision. I did not commit deliberate misconduct in regard to my job performance. I did my job to the best of my ability. I wish to appeal this decision." Got it? Okay.also say, "If possible, I wish to request an in person hearing concerning this matter." That is all you need to say. You need to put in your telephone number so they can reach you to set up the hearing.
I suspect you are sitting there reading this letter and whimpering because they didn't love you, didn't find in your favor. Buck up. Sit down and begin to make an outline of everything about this situation.
Perhaps it can start with something like, I begun working for this employer on such and such date. I told him at that time that I would be relocating in ....months when my military husband was transferred again to a new location.
I was not, at the time of my employment, given an employee handbook. In fact, I had no idea a handbook existed, had never seen one until...such and such date, when I was presented with this handbook, after I had been written up and threatened with termination.
I was given...amount of training. My training for the job was done by**************.I was able to learn what was required of me and do what was required of me, and I always did the job to the best of my abilities.
DO NOT BE STUPID. Don't pop up and volunteer, "Yes, I made mistakes....whine whine..." Say you tried your best and if you made any mistakes, you immediately when you received feedback changed your behavior and ALWAYS did the job to the best of your abilities.
Let them show exactly what these mistakes were, that they were deliberate, and that you were doing them knowing you had been warned not to do them, and knew you could be fired for doing them. Don't say negative things about yourself in the hearing, even in the name of being honest. You will find that your employer will have no trouble shading the truth to his advantage. But you do not argue with them. You just tell your story as you know it to be true. You must be the most believable.
You will want to point out that your "job performance deficiencies" increased sharply and abruptly when you went to your employer and told them you were pregnant. You may be able to say that until this point, you had never received any feedback that you were not doing a good job (had you ever had a performance review or a raise or a word of praise during your tenure there?)
That when they began to be so unhappy with your work, that you tried as hard as you possibly could to please them and change anything you were not doing right and tried to do a good job. This would be a good time to mention that you received the handbook, the write ups, and the counselings all in the short time between the time you told them you were pregnant and the time you were terminated. Stress that your performance of your job performance had not changed,that you were doing the job as you had in the past and it had been quite acceptible, UNTIL you were found to be pregnant and would be leaving soon.
Yes, this is standing up for yourself. This is not something that someone else can do for you. You must not decide to wimp out on this. You have absolutely nothing to lose doing this appeal, and a great deal of self respect to keep.
Get your material together, and then let us have another shot at fine tuning it. This is sort of like a presentation you're doing for a class or something, you're going to be well prepared and professional, and you will have a pretty good chance to win.