I [M22] may have pushed away my girlfriend [F19] of seven months in one phone call. Advice needed.?

Details: My girlfriend and I have been together since March. She is 19 and I am 22. Mary is a sophomore in college and I am a college graduate planning on returning to graduate school in a year. Our relationship has been long distance since the middle of August, with her being 1.5 hours away. I visit her two to three times a month.

Our relationship: I have never known love as I do with her. Mary understands me in a way that no one else in the world knows. We have started to speak of marriage and even of the kids we would have. We have a mutual sense of humor that causes both of us to laugh together for hours at a time and we connect spiritually, and there is no one else who makes me as as happy as she does. Mary has said the same and has shown her love for me too.

What happened: A couple of nights ago, Mary and I were on the phone talking in the late evening. I had just come home from work and we were having a delightful conversation as always. Mary was telling me about her day and how she had also been so excited to receive my written letter to her in the mail. We were both super excited for the weekend, when I would be coming to visit her and because Mary wanted us to celebrate my birthday belatedly together.

Towards the end of the conversation, I told Mary that I had to leave and wake up for work in the morning. Right away, her tone changed. Her voice became sad and I could tell she was emotional. I asked her what was wrong and to talk to me. She said nothing was the matter and that she would be fine in the morning. Mary genuinely sounded emotional. This had happened before, but the first time it happened while we were apart by distance.

I refused to hang up the phone out of concern. Mary started to cry and would not say anything besides the fact that she "would be fine in the morning". I continued to stay on the line, continued to ask her, and it was not until some time later that we did hang up the phone, with her crying audibly on the other end as we said bye and hung up. Afterwards that evening (10-15 minutes later), I send her a text saying that I am always there for her, and that her worth to me is infinite, and that I love her.

Since then: We have not spoken. I have not heard from her. I sent her one text in the morning after to tell her that I had to cover an early shift for work in the morning, and that we would not be able to wake up together and have our morning conversation over breakfast as we do when Mary is at college. No response at all.

My Mistake (?): Mary has said before that she does get emotional at times and will start to cry for no reason. She has said it is a mix of hormones and that causes her to make a bigger deal out of things then they really are. This has happened before, and always I have respected her space and did not press her any further.

Did I make a mistake in pressing her further? Part of it is the fact that we are long distance - I wanted to "make up" for the distance and be there for her and to talk. I wanted her to open up and make her feel that even though we are miles apart, that if Mary was struggling with something, that I would be there for her. I feel that I should have recognized that asking her and not hanging up the phone only stifled her and suffocated her, when she simply needed a good cry.

Request: Did I do something wrong? What do I do now? Should I wait before contacting Mary? Should I wait for her to contact me? Should I apologize for what I did, acknowledge that I did not give her space? What should I say to her?

Thank you for your time, I really need the help as I am so uncertain and hurt right now.