The feelings of jealousy and fear of things like an SO looking at another, stems from insecurity. It can be a tendency in BPD because we are not secure in ourselves, due to the lack of identity. yes many do think this way.. I have myself but I do not consider it good or acceptable for me. It is something to work on, but not working on "not thinking that way" but working on your own confidence in yourself and the relationship.

I'd try focusing on the fact that you don't expect him to cheat. When you fear, or get jealous or bothered by his looking at a magazine like that, try to re-direct your thoughts to how you really do trust him, but that he's not "blind" and is going to see and take notice of women that are attractive. That's natural. A man may notice another woman is attractive but that does not mean that he wants or expects to replace you with her.

Hope this helps.
~S4