My bf (M39) won't let me (F27) do a half marathons because of fears that I might die. What to do?

My bf (M39) and I(F27) have been dating for 4 years. This is my first serious relationship, he is divorced. We have been training for a half marathon together. We both have about 3 months left on our training plan and we both do fine. My bf has, however, been in a panic attack and very worried about my health after a bad workout we had almost a month ago. He has researched that too much cardio can lead to death. He wants to add strength training to our routine and he wants me to stop with the long runs, because the only thing that matters to him is that i am healthy and safe. I want to do the half marathon, because I have already done the money and the effort and wanted to have done before we are thinking to have kids. I feel like this is a one time thing for me and I resent my bf for trying to keep me from achieving my goals. I am not sure if I can end the relationship over this? I understand that it is because he cares for me, but I can't let him hold me back on everything that I do. What is the next step in this situation?<br><br>Tl;dr My bf wants me to stop with a half marathon I am training for because he thinks it is bad for my health. I want to do the half marathon, because it is a life goal of mine. What to do?