I'm looking for some advice for myself [20F] and my boyfriend [18M].

I'm a 20-year-old woman, and I've been with my boyfriend, who is 18, for the past 10 months. When we first started talking, he had just ended a year-and-a-half-long relationship and was still coping with that loss. Before meeting him, I was flirting with another guy who was interested in me, but I was doing it for attention. Once my boyfriend and I started talking, I stopped the flirting, but the guy kept pursuing me despite my rejections; I merely wanted to remain friends with him as a distraction because I was insecure about my boyfriend potentially leaving me for his ex. I was worried this might happen, especially after a few days before a significant argument, when my boyfriend mentioned that his ex had reposted a TikTok about someone random and asked me, "Is it over for me?" He also brought up his ex multiple times during our conversations, which I understand since he had just come out of that relationship. This situation made me feel insecure. When I mentioned needing a distraction, I meant I wanted to hang out and play video games together; it wasn’t about anything romantic or sexual. I eventually ended up cutting the other guy off, but it took a fight with my boyfriend for me to do so, and I regret that. It wasn't that I had feelings for the other guy; I just feared losing my current boyfriend and would miss having that distraction if he chose to go back to his ex. I also have a tendency to flirt for attention and validation. This history has led to many arguments between us about my past actions and insecurities. I've realized that if I had communicated my feelings about not receiving enough attention and affection from him sooner, we could have avoided a lot of this drama. I felt insecure about the frequent mentions of his ex, but I also recognize that he needed time to grieve and had suppressed his emotions. I've struggled with effectively discussing my feelings; in the summer, whenever I tried, my concerns were dismissed with comments like, "What do you want me to do about that?" or "Well, suck it up," making me feel unable to express myself further. Despite the time that's passed, I've occasionally fallen back into avoiding my feelings, and I'm not sure why. I realize I've manipulated him unintentionally because my actions sometimes communicated the opposite of my intentions. We've had significant arguments over this and other issues, and we’ve both expressed thoughts about leaving the relationship, which I want to avoid. Ultimately, I really love him and want to hear your thoughts on our situation.