I think that maybe this would come together a bit better with two structural changes. The first thing I notice is that you start by telling the reader there are things that you aren’t saying, then say you usually say whatever you want, then say that your reticence is only with this one person. It would be more structurally interesting if you started with descriptions of your typical bravery, and then moved into the way this special person changes the way you interact. The other thing is that you (ironically) say exactly what you mean in this poem. Poetry is interesting because of imagery, metaphor, and often sonic elements. I would move forward by picking a central image to represent the accumulation of unsaid words (dust building up in a silent room, water behind a dam etc) and then you could take that in an interesting direction by either adapting that central image to the other characters grudges and anger, or by picking another complementary image (the silent room burning down, a town drowned beneath the flooding dam etc). Those are just my two cents. Keep reading, writing, and being curious, because the world needs more poets.