She’s beautiful and I’m insecure!

My girlfriend is extremely beautiful, and this causes a lot of issues because it makes me feel constantly insecure when we are out in public. I always assume people are staring at us and wondering why she is with me, and this makes me behave differently when we are out than when we are in a private setting. I know this is unfair, but I can’t figure out a way of dealing with this, and don’t know how to explain it to her. I am worried that, at some point, she will just realise it’s too much work being with me and leave me. She is not a shallow person and I love her a lot, but this is a recurring fear and I feel helpless to stop it. How do I cope?
It is definitely a problem you need to address because it seems as if your girlfriend isn’t doing anything to make you feel this way. Insecurity is real, and can be crippling, but recognising that it exists and can be managed is the first step. If you love her, and she feels the same way, that ought to be the driving force behind anything you do and how you choose to behave. You should also acknowledge that your insecurity is unfair to her and doesn’t justify how you treat her. Mutual respect is critical for any relationship, and you should consider speaking to a professional if you can’t find a way of resolving this on your own. All you need are the right tools.

I don’t know if this is something I should worry about, but I found out that my ex-girlfriend has been spending a lot of time with one of my closest friends. Should I tell him to avoid her, or just mind my own business?
Your relationship ended for a reason, and your ex-girlfriend and friend are both presumably adults who are free to make their own decisions. Why not speak only if you are asked for advice?