stopped somehow and now. You have to ask your girlfriend out of just getting to know what is happening exactly. I'm not asking you to go insecure, not trusting her or question her as if there is something really going between the two.

Tell her that there is something bothering your relation with her recently and that thing is someone is showing interest in her.

Don't jump into conclusions and just look for answers or reactions from her. If she looks fine as if she is aware, if she does not give a damn to the guy, if she is just ignoring or him or if he is bothering her in different ways or place other than office through different communication ways.

Check if what is happening is drawing her attention, she is aware of it or not. Any idea what does that guy wants from her? Because it seems that he won't stop ... he might thought that picture means something to him while it does not to her.

Is he aware somehow that you two got something or you are just too good in hiding it that he does not know? Can you ask her is she told him something like I have a boyfriend and he knows somehow that it's you?

If he knows then he might be up to something so be careful of what might happen next. It's kind of difficult from your side to do something if you both are trying to keep that a secret, but it would be easier for your girlfriend to find a way to shut him down.

I don't really know what kind of guys would ask and beg a lady to go out on a single date with him while she is telling him: I have a BF? Indeed he is one big jerk ...

Do not dwell in the past, do not dream of the future, concentrate the mind on the present moment. (Gautama Buddha)