Struggling with first relationship, don't know where to go...

Going into college, I had never been in a relationship. I gradually formed a stable friend group and started to spend more and more time with one of the girls. At first, I was treating it as a casual relationship but it was clear that she loved me early on. Over time, I grew to reciprocate her feelings as I found her to be fun and she made me happy. Our relationship was weird because we didn’t meet each other through dates; we were already in our own college friend group bubble. Also, she would spend so much time in my apartment and sleep over that we were practically living together early on.

Now that we have graduated college, however, our relationship has been more difficult. She had revealed to me a few months before graduation that she was suffering from severe depression. I had no experience with depression so I was not really sure how to handle that, so I chose to accept it. She meant a lot to me and so I wanted to be there for her. We were accepted in different jobs and had to live a few hours away from each other, across the state. We decided to commit to a long-distance relationship where we would alternate weekends visiting each other.

My problem is that I’m having a really hard time figuring out what I really want. I am at weird stage in my life where I have a lot of decisions to make as a young adult who just graduated. I have grown to love my job and want to spend as much time as I can to excel in my career. That is hard to do in a long-distance relationship. I don’t know if it is best for me to break off and completely focus on myself or to continue and commit to my first ever relationship. Also, seeing how this is my first relationship, I always seem to have a thought in the back of my mind to break off and explore other options and gain experience in relationships before settling down, which in turn makes me feel awful because my girlfriend is such a sweet person. Most of all, I am worried that if I choose to break up, she will slip into severe depression again and that’s something I would never want to cause. Please, can anyone help me figure out what’s best?