I (29M) have been with my SO (28F) since we were in high school. I love her dearly and have total respect for her, as she's my best friend and our lives are deeply woven together. Having began dating at 16,17, I am the only person she has ever been with. She's very much in love with me and has only ever had eyes for me.

However, I have very strong desires to want to talk to other women, and expand my sexual experiences beyond us. We've discussed the idea of involving a 3rd, or me simply experiencing someone else over years but despite being an open minded person, she's still not open to the idea. This desire hasn't faded at all in the past decade or so, and sometimes i fantasize about breaking up with her so i could experience this, but her heart is too pure and she would likely be damaged from it. I feel like i'm crippling myself socially, not allowing myself to talk to girls so i don't get put in a situation where i am tempted to cheat and sometimes it hurts my heart to see these beautiful women i can never talk to. I promised her I would tell her if i ever decided to cheat, and we've always had a brutal honesty policy.

Has anyone experienced a situation like this that can share some advice?
Would the relief of a brief affair be worth it? Would a temporary breakup be too crippling for her heart? She already has anxiety problems.