Just saw my ex with another guy, that hurt

As title says i saw my ex with another guy today in a supermarket. Its been nearly 3 months post break up and that's fucked me a bit i won't lie. It hurt a lot just seeing her with another guy but it's also confused me as she blocked me last week on insta and literally unblocked me yesterday and it just gives off like she's not over me but yet she's with another guy? My heads gone