Oof I wouldn't advise a coworker with an interesting new position and career direction to prioritize the BF, personally. Shouldn't he be flexible to supporting your work schedule? If you would do that for him, but he can't do it for you, I especially would not prioritize his feelings.
Sounds like you're not even doing night shifts yet. If you can, don't create problems for yourself by stressing about the future. Maybe it will be different than you're imagining. Some places have day shift positions open up for night shifters within a year. Is that the case on your unit?
Or, if anxiety is often a problem for you, maybe your job has EAP or covers therapy. It sounds like you had a rough patch before this job, too. Sometimes it's hard to know how much therapy can help before you try it. It may surprise you.
In your post you say this job felt like "what you needed". That's great! Congratulations. In my view, temporary bad schedules are worth a job like that. Plus on night shift, there's plenty of time to really understand what's going on and study a new workplace. (Also, usually the people are chiller ?) Enjoy and again congrats on your career success!