The speaker is stuck in confusion about love. They can't tell whether they love their partner or whether they are loved back, and the short, simple lines make that uncertainty feel raw and unpolished, much like the title, "this is a mess," suggests. The speaker points to hurtful behavior that contradicts the words "I love you," yet admits that feelings are there on both sides: "Because you do. / And I do."
Midway through, the speaker tries to work out what love even means, and says they're trying to be what the other person needs while staying true to themselves. Then comes a list of small, tender details: dimples, freshly washed hair, a partner who sleeps through everything. These seem to be the proof the speaker can trust.
The apology, "And I'm sorry," sounds heartfelt, which makes the final line, "NOPE FUCK YOU," jarring. It suggests the speaker's anger or frustration breaks through the tenderness. The mood is honest, tangled, and unresolved.