How do I handle this?

Recently me and my boyfriend had an argument. This argument was based off of something that had been brewing for a month or so.

During the argument he was very defensive and kept walking away. I felt as if I couldn't fully express how hurt I was by the discussion. A few days later we had another argument and again I felt the need to reserve how I felt so as to not escalate things and keep his feelings safe..he eventually left that night still within argument and I cried myself to sleep.

Now we have worked through both disagreements and moving forward but..I'm having a problem. I love him and I want this future with him but I feel guarded. I'm fearful of the next time a discussion will go wrong and I feel as if I never got the opportunity to be upset.

How do I go about discussing this with him and maybe you ladies could help me understand why I have the urge to "feel my feelings" if we've moved on?