Feeling insecure with my boyfriend? Do I need help?

Recently me and my boyfriend moved in with his friend, as we didn’t have any other options. I was nervous to do so because his friend sleeps around and brings new girls home often and was worried my boyfriend would see that and think that behavior is cool and want it too. My boyfriends friend does bring hot chicks over often with their perfect bodies and it makes me feel so insecure and ugly around my boyfriend. Last night we were talking and his friend says “can we talk about how hot so and so is?” Trying to get a reaction out of my boyfriend. My boyfriend didn’t say anything but I know he would have had I not been there. I got upset and told my boyfriend that I feel ugly and don’t know how I’m supposed to compete with that. He reassured me that I have no competition and he wants me forever. I know my boyfriend gets tired of me getting upset over my insecurities and don’t want it to ruin our relationship. What do I do, why am I like this and so insecure?