That sort of behaviour by an adult is predatory, online or not. If, by chance, the minor was lying about their age (which is easy to do online) then you couldn't really blame the adult.

But if the adult is aware of the age of the minor, then it is predatory. Minors can't be expeted to fully understand the situation that they find themselves in, and are suseptible to grooming behaviours... a training/brainwashing of the minor to get them to participate in sexual acts while feeling like it was their decision, or like it's the only thing to do to keep the approval of the older adult.

There is nothing, absolutely nothing, wrong with you talking about your experiences with a therapist. If it is bothering you now, then it is worthy of talking about. A lot of the time minors don't realise what they experienced until they are older - hence why many survivors of sexual abuse don't talk about it until they are older. The whole point of the grooming tactics is to make the minor believe that they had as much control as the adult, and to confuse the minor about everything to help ensure that they don't come forward or put up a fight.