This does sound similar to what I experience, and I made a small post about it recently. I'm not too sure what to do to avoid these outbursts. Some people find very little to no irritability when hypomanic, whereas others find themselves irritable frequently. I haven't discovered any ways to avoid it - I've always had to just suffer through it and wait for it to pass. My boyfriend is incredibly supportive of me and helps me to calm down. From what you say, your boyfriend is also very supportive. I think without that support, these meltdowns would be even more difficult to get through. But as you realized, they do pass. Hope you're feeling better now