First of all, go get a physical and explain what’s going on to your medical doctor. Since this is new behavior, you may have a new hormone imbalance or some other medical reason for your short fuse. So, rule out your health as a reason for your snapping.
After you do that, and if you find that this is all emotional, and not physical, you’ve got to figure out what’s really going on, because what you’re describing aren’t primary reasons for your anger — especially if things have been fine for 2 years.
I can only begin to guess at possible reasons you might be upset. Are you angry that he hasn’t proposed marriage after 2 years? Are you upset about something going on in your own life — like your work, your weight, your family — or something else that is upsetting you, and rather than deal with that problem directly, you’re misdirecting that anger on your boyfriend?
I’m sorry I can’t help more, but I can tell you that your problems have to do with something other than what you’ve been able to tell me here. Dig deeper. And let me know how things go.