my boyfriend (20M) told me (18F) he wants to have sex with other girls?

i dont even remember how the conversation started. it was about threesomes and he said he'd like to do it. i asked him straight out if he wants to have sex with other girls (without me involved) and he said "kind of". (btw he is fully aware of my crippling self esteem) hes acting like its no big deal and its natural for him because "im a guy" and he just has the urge to "spread his seed". but idk im kind of hurt.. hes justifying it by saying that "at least hes being honest" and "he'd never lie to me" and that he wont do it if im not okay with it (which im not) but now i just cant look at him the same. especially after i suggested the reversed situtation (me sleeping with other men) and he said "i would never share you" and "i own you" idk i think he was trying to be hot or something but instead i just cringed and got really offended. i feel like he sees me and every other woman as an object. ive expressed my concerns to him but he doesnt really get it. chat am i too sentitive or is it over