Not sure how to articulate this to my boyfriend, why I need a career change..ect?

no, you're simply acting on your desires, which at times is a good thing. in this case, i see no problem with you doing what you want. sure, you could make a lot of money continuing in your career field, but simply imagine yourself in 20 years in the same field. do you even want to think about it, or does the thought sicken you? your significant other is upset because it means a compromise in his own lifestyle, which is never easy to accept. it is not selfish to act on a whim, especially when it concerns your own long-term happiness. you are asking for advice because you already know the answer. follow your heart, and hopefully everyone else will understand. if they love you, they will accommodate you.