About the relationship
My girlfriend and I have been together for 5 years now and we have lived together for 2. We are both introverts, and we had some trust issues over two years ago, admittedly my fault (watching p*rn videos if useful to know). This is my first relationship, and it's her second (the first has gone bad, since the other guy fell in love with another girl, and they broke up the very next day).
Similar to How to tell my girlfriend I'm uncomfortable with her getting jealous when I look at other people?, so I'll try to add more details as possible.
It's related to bumping up into other girls when hanging around. Example: in summer it's fairly common to see girls wearing (or "not wearing" as she used to say) shorts/hotpants. In winter pantyhose/leggings are addressed.
No matter where I look or what I do, I get accused of staring or wanting to leave her for "one of those". She becomes REALLY aggressive sometimes, shouting and insulting for a while, pretending that I had to keep my eyes closed, or walk behind her (my gf), and such. The really frustrating part is that I can literally stick my eyes to the ground but she insists that I'm giving nasty looks at the girls.
This is really affecting our relationship and our lives, since she doesn't trust me to go alone to the supermarket anymore.
It might be addressed as jealousy, but since I have no female friend (only acquaintances) I can't tell that. My real concern is related to her very low self-esteem, maybe because of her previous relationship, or the continuous "appearence competition" with other girls. (she's following a strict diet to lose weight but does't succeed IMHO because of too much stress, and that is really causing her more frustration)
How I tried to manage the situation
Badly. I already tried to discuss the matter with her by:
Trying to explain that I am not interested in other women. Furthermore I'm only sick of such random encounter which create unnecessary fights.
Trying to compare our behaviour with our friend/acquaintances in a relationship.
Asked to propose some solutions that would satisfy her but the answers where unfeasible. Example of proposed solution: "stop where you are when you see one and turn the other direction".
To make everything worse each confrontation we have on the matter could easily escalate into verbal and physical violence, so upon the next encounter I become visibly stressed, and her interpretation is that I'm trying my best to not fall for the other girl.
Sorry If I complicated too much the explanation, if needed I will add/remove details. Now the question (edited to just one):
How can I tackle the situation, possibly by making her understand that I'm not interested or attracted by other women just because of their appearence?