Threatened to be Fired for "patient safety" issues.

Hi, I am a new grad looking for some advice or opinions on this issue I am having. I have been working for 6 months at a hospital and have been having some problems there. At my interview, my NM for some reason told me that it annoys her when people call in sick to take care of their children and questioned me about my race because I have an ethnic last name. I thought she was strange, but decided to accept her job offer anyways a couple weeks later. Anyhow, I discovered I was pregnant with my first child shortly thereafter. I felt it my duty to inform my upcoming NM about the situation and she was very apprehensive, asking me how much time I would need off for leave and if I still planned to work full time day/nights. I told her not to worry, my job would come first.
Once I started orientation, my doctor placed me on a 25 pound weight lifting restriction due to the pregnancy. My NM told me that if I brought in that note, I would not be able to work at all because I no longer fit the job description of being able to lift a minimum of 50 pounds. I consulted with my union and then opted to not bring in the note.
Shortly thereafter, I was rear-ended by another motorist on my way to work and placed on a 5 pound weight lifting restriction for 2 weeks. My NM was less than pleased. She placed me on leave without pay for that time. She said she probably could have accomodated me, but was not required to, since it wasn't an on-the-job injury.
Needless to say, I was not on my NM's good side. I was also exhausted from my pregnancy and not always feeling well. However, I dutifully came to work everyday.
After working with a preceptor for 2 weeks, I was placed on my own with the most difficult patient on the floor. I made a medication error at this time. I did not know the procedure for removing fentanyl patches and removed one early. After that, I was placed back with a preceptor for an additional 2 months or so. I made one more medication error (gave wrong dosage of tylenol) and then made a medication error in conjunction with another nurse. It was another nurse's patient and she had set the IV pump to end early. It was the night shift and I didn't see that there was still about 75 ml of medication left in the bag as it was also covered with foil to protect it from light. This was over the course of 3 months or so.
During this 3 months of orientation, my NM suggested that I look for jobs elsewhere and that the other nurses did not like me. She told me there was no positive feedback about my performance. I knew that there had been, however, because I had feedback from other nurses who told me that they had gone to my NM with positive feedback. At the time, I told my NM that I was not going to quit and that I felt she was creating a hostile work environment for me. She let up and gave me a positive review at my 3 month review, saying that I was "right where I needed to be".
Things were going well for a couple months. There were a couple times that I didn't know the policy for my floor regarding certain situations. For example, I didn't know that after a patient falls, we were to institute neuro checks every 15 minutes for so long and then every 2 hours for so long. I also didn't know that insulin would have to be double checked by another nurse to avoid giving the wrong amount.
But once I made one mistake, especially a procedural mistake, I never made it again. I always learned and never did something the wrong way twice. I put a lot of effort into my nursing practice. Later on, I ended up disconnecting a patient from an IV for a half hour to take him to the bathroom, then found out I wasn't allowed to do that.
About a month ago, my NM accused me of making some kind of boundary violation with a patient because I had visited him during my shift to see how he was doing while he was on another unit temporarily. The patient confessed that he had a crush on me and I told the charge nurse, who rather than advising me to no longer accept him as my patient, told my NM that she felt that I was encouraging him. Turns out she advised me incorrectly and I should have refused to work with him again after that. I went to the union about this and they totally reamed my NM out. About a month later, I gave Vicodin to a patient too soon after he'd had his last dose and my NM put together a packet of allegations and threatened to fire me.
I was told by other staff recently that my NM had been collecting this information from day one, asking people to write down mistakes that I made. She kept a personal file on me and then denied me access to it. A couple things in the packet were never brought up to me. No positive information about me was included in the packet.
So, now I am up for a hospital board hearing to determine my future with this hospital. My feeling is that I've made mistakes, but none of them has been serious. The last one was probably my most serious mistake because rather than giving this patient another dose of vicodin, I should have called the doc to ask permission. That one is probably inexcusable, but the others I feel were genuinely education-related.
My gut feeling is that my NM has not liked me from day one and the fact that I have made mistakes has been great for her because she's been collecting evidence. She doesn't like the fact that I started pregnant, that I've gone to the union several times, and probably just plain doesn't like my personality.
So my question is, have I really been that unsafe that I should be fired? How many and what sorts of mistakes do new nurses generally make? I really want to learn from this experience and have been doubting my nursing practice. Thanks.