How to tell if my boy bsf of 5 years likes me?

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Just to clarify I've only just started to think he likes me due to the fact we're constantly together in uni like we're inseparable and he is my partner in any class we have together. Our hands tend to graze eachothers a lot and we have subconsciously touched eachother more than usual in a jokingly manner (I think). And one time I brought up a boy I used to talk to and I didn't tell him about he said "why didn't you tell me" so I don't know how to interpret that
How to tell if my boy bsf of 5 years likes me?
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