It has nothing to do with their career. I'm 22 and I have been dating a med student for 3 years.
The most important thing is an open dialogue, as you say, and utmost respect for the other person. But I also know that He loves us so much that He would never take away our ability to choose for ourselves.
At the risk of overloading this post, I'm going to copy and paste here, a Reddit comment that I made in this exmo sub the other day.
If I were you, I would sever the relationship and find someone else. It really has been helpful.