personal relationship troubles

I have never been one to get insecure or sensitive about small things my partner does in a relationship. I’ve always just been very carefree and not worrisome in any ways. However, with my current boyfriend, something has been weighing on me for a while. Im not liking who I am with him. He’s perfect in my eyes, hasn’t given me any reason not to trust him, but I’m starting to get very hyper-sensitive about different things. I cried about one of the the women he was once with and it still loomed over me after he comforted me and literally has no contact with her. I don’t know what it is. I love myself, truly, and I’ve never been with someone like him who genuinely cares about me the way he does. I just dont know why I’m acting this way. Is it BECAUSE of how much I care and don’t want to lose him? I don’t like how it makes me act... I feel like I’m being so stressful on him :( help please