While you are discerning your vocation, it may conceivably be a “near occasion to sin”, in that kissing may conceivably lead further, to actual sin (fornication). But for the kissing itself, I believe it not to be sinful, even in the context of “dating” as popularly understood - as divorced from “courtship” (dating for the purpose of marriage after the discernment of a vocation [after all, how can one date with an eye to marriage, if they are discerning their vocation, and may not marry?], which some Catholics less fundamentalist than myself, even, believe is the only acceptable form of romantic activity) - with neither activity being inherently sinful, although both being possible near occasions to sin.
A near occasion to sin is no more of a sin than the concupiscence or sin-nature that remains after baptism is itself sinful; it is inclined to sin, but not in sin (at that instant). A sin’s sinfulness is imputed to the sinner only when it is acted upon or actualized; not when it is thought about, and merely a potentiality.
Now, a word by way of my personal opinion, myself speaking it: It seems to me, that the less the kissing is contextualized in to a romantic relationship of some sort, the more likely it is to be sinful, I believe, as also it is more likely to be a direct prelude (not so much a near occasion) to sin, as in the one-night stand.