You feel it building on your side, and you are trying to tell whether it is landing on theirs. In something undefined, that uncertainty is its own particular kind of ache.
Short answer: yes, people do catch feelings in situationships, including the person who seemed most determined to keep it casual. Keeping it light and developing feelings often run at the same time. The closeness you feel is real; their inner life, though, is only ever visible from the inside.
The same behaviour, the warmth, the pulling back, the mixed messages, can come from someone falling for you or someone holding themselves back from it. Reading their feelings off their actions rarely settles anything, because the actions are genuinely ambiguous, and trying to read them from the outside is part of what keeps you stuck.
Whether they have caught feelings, and whether feelings would change what they are willing to build, are two separate questions. Someone can care and still want the arrangement to stay as it is. Finding out directly is the only way to learn either.
Say your side first, plainly, and then ask: "I have caught feelings. I would rather know where you are than keep guessing." It is honest about you, it keeps your footing, and it invites an answer instead of another round of signals.
Go deeper
Why You're Still in the Situationship gives you the psychology of why you are stuck, the assessments to find out where you stand, and the exact words to get clarity, commit, or walk away. Five profiles, full-page assessments and a complete script library.