He’s my first love, but I’m not his

My boyfriend is my first serious relationship, and the first person I’ve truly been in love with. On the other hand, he’s had a serious relationship before with his high school sweetheart who also happens to be the girl he lost his virginity to. I’m 22, and I missed out on a lot in high school (dating, prom, parties, etc.) because I was deeply depressed with social anxiety, and sometimes I envy and resent others like my boyfriend who have had those experiences.

He only dated her for 8 months, and says he was so in love with her for most of it, but it look him 6 months to say, “I love you” to me. He says it took him 2 years (up to only a few months before he and I started dating) to get over her which is longer than we’ve been together (going on a year and a half now).

It may be due to the way I was raised, but I feel like my heart, or my love is something that you give to someone. I gave him my heart like I gave the person I ever had sex with, my virginity. I sometimes feel like he doesn’t appreciate what he is to me (my first love) and that I’m giving him more because he can’t possibly give me his whole heart like he gave his ex. I know it’s immature for me to get mad at him for having loved someone before, but I just can’t stop feeling upset over it.

When I was telling him how I felt, he was looking at his phone the whole time, and then he tried to make me feel better by cuddling which lasted all of 1 minute before he started looking at his phone again. I just worry that he doesn’t love me as much as he loved her. When he told me he only got over her shortly before we started dating I took it as a red flag. Am I wrong for that? He said he couldn’t get over her until he found something better which is me, but that didn’t sit right with me. When I told him I didn’t like that, he retracted, but I knew that’s what he meant.

TL;DR: My boyfriend is my first love, and I’m not his. It’s making me feel insecure, especially when coupled with the fact that he sometimes doesn’t give me the care and attention I feel like I deserve. How can I get over these feelings of envy and jealousy towards his ex which I know are immature and unhealthy?