Definitely talk to him about your concerns but do it in person rather than through text. If there’s one thing I’ve learned, it’s that serious conversations like that should be avoided through text because it’s hard to convey tone. At the very least, talk to him over the phone if you decide not to see him in person, but I think your concerns are valid otherwise. Does it say when he signed up for the site? Is it possible he did it shortly after you two broke up as sort of a rebound, “getting back out there,” type of thing or has he been active on it recently?