Is this considered to be stalking?

I recently followed a girl I knew from uni (we all finished last year) on Instagram. We weren't great friends to be honest, more like acquaintances, but I was pretty sure she had a crush on me. I really really liked her but at the time I was dating someone else which has now ended. She hasn't blocked me or anything but she hasn't followed me back. If she had followed me back I would have messaged her but this has made me uncertain. Also I have had so many rejections messaging girls I don't like doing it anymore. From her photos it is clear the part of London that she lives in (it's about half an hour on the tube from me) so at the weekend I went and sat outside at a cafe in that area for an hour hoping to maybe see her. I didn't see her and went home. I told my housemate and he said I was a massive stalker that needed help. I mean is that really true. I feel awful about this to be honest.