The speaker is carrying a secret they can't share, and it is slowly wearing them down. Something happened that they wish were only a bad dream, but they know it's real, and they say "we are both to blame," which suggests they feel tangled up in guilt and shared responsibility. The poem never says what the secret is, and that silence is part of its effect: the reader feels the same locked-up pressure the speaker does.
The speaker tries to cope in painful ways. Alcohol is meant to "wash it away," and cuts are meant to make it "disappear," but neither works, and the fear stays. At night the speaker lies awake asking "what if what if," and the repeated phrase sounds like a mind going in circles. The short, plain lines and simple rhymes make the poem feel raw and unpolished, almost like a whispered confession. The mood is heavy, anxious, and lonely, with a sense that the speaker is stuck and badly needs someone to talk to.