Boyfriend is taking his stress out on me

I’ve been in a relationship for over two years and it has been mostly great. Recently, we started a business together and he has been more condescending and mean. I’ve been coaching myself but I’m getting to the point that I just want to leave, but I also don’t.

How can I process the negative words (my adjective, I know) in a way that will benefit us both? For example, I’ll ask a question and he will roll his eyes, sigh, and say something like “I already told you that.” It’s frustrating. I work full-time as a physician and he is managing the start-up of the business.