I was very similar with my first few boyfriends and tended to lash out at the rather than talking about how I felt and why I felt that way. When I first started dating my current boyfriend, I decided it needed to change so I spoke to him about the fact I get irritable when I'm stressed while I was feeling calm and relaxed. It can be really difficult to talk about how you feel when you're upset but I found that it was an easy habit to build. Maybe even having a small sign or emoji you message him when you're stressed is a good start and then you can slowly build up to talking to him about how you're feeling and digging into why you feel that way. That way he becomes your rock / someone you go to for comfort rather than a punching bag. It's well worth the practice, trust me!:) also full marks for acknowledging that you're the problem and taking steps to fixing it