Posted this before just wanted to add more details.

I M20, have a gf of 3 years. She has a massive libido and she has told me many times she would have sex with me all day if she could. Recently I have been getting more into cuckoldry and have been fantasising about her having sex with bigger more muscular men that can in my mind give her the sex life she craves. I have developed a humiliation kink and want her to humiliate me. I have even fantasised about more extreme stuff like forced bi. For context I am really not small or anything I am 6 foot with a 7.5 inch dick and pretty thick, she is a bit of a size queen, she loves it when we roleplay cnc and that kinda stuff, she also told me many times she likes it when she feels that I am stretching her. This has only made my fantasies more real because I want her to really be stretched out by a monster. I don't know how to approach this with her, I thought of maybe getting her a dildo and playing with that or maybe start with a threesome MMF, or maybe get her to sext with a guy online or smth. I am worried though, I feel like it will ruin our sex and the way she sees me. She has also mentioned cuckoldry before but more in the context of how hot it would be if I had sex with a girl in front of her, I just don't know how to approach this or even if I should. I am just curious what you guys think I should do. I am very conflicted, I'd like to hear your thoughts/advice. And just curious how many men are in similar situations.