Should I really think about my own mental health because of my boyfriend's disease?
Of course! Are you have mental health issues as a result of your boyfriend's disease?
We all have problems to cope with.
It is good to acknowledge your mental health and address it.   It is also advisable to realize that both of your situations may be different so that you do not drive a wedge between the both of you.
Nah, I don't care about that. I'm going to cry about it when I want to.
Crying is a great way to let out emotions. It's never good to dwell and bottle up emotions. You are a strong person and really know how to address mental issues, but just know that I am here for you if your boyfriend's situation is too much for you to handle and you need someone to talk to.