Past Issues and Dark Secrets between (17M) and (17F) couple

TL; DR: I think that my girl is not happy with our relationship but pretends to be. Also her past makes me really insecure about her added to the silence we have between us. I also got some dark secrets which may end our relationship straight.

I know we may be much younger for a relationship between (17M) and (17F) but it feels right. This is my first Reddit, and I am posting here because I genuinely need help. My girl is great. I love her a lot and so does she. We have been in a relationship for 5 months but still never talk to each other face-to-face and only on Instagram even though we are in the same classroom and go to school by the same bus. We both got very strict parents so there is no way we can meet anywhere else in real life.

She openly tells me about her past crushes, and she had 6-7 of them. I too had 3 crushes in the past, but she got almost double. She also got a celebrity crush and may talk to boys without any hesitation. All this makes me very insecure. Otherwise, she is really nice hearted, and I really want to continue this forever. I don't want to open up about my insecurities, for I don't want her to know anything that makes her sad. I even vowed to myself not to let her know anything that makes her sad.

But last month, I told her about my habit of watching p0rn and m@$turb@ti0n to which she said that she didn't think I was like that but accepted that and even helped me get out of these habits. But then I got $exual feelings about her which made her feel really bad and unsafe. I can never see her being unsafe around me, so I sadly proposed a breakup. She said that although she was very sad, she didn't want a breakup. After much debate, we agreed and continued the relationship. But something tells me she isn't really happy. If I ask her directly, she never tells anything and just says she is very happy, but I feel the other way.
Also, as she shares every feeling and secret she has, I too got one but it's very shameful. In the recent years, I even m@$turb@ted imagining my family members, sniffing their innerwear and even touching one member at a wrong place while she was asleep. I want to share all this, not to share my guilt, but to make her know everything about me. But I feel what would she feel on hearing this and so, I don't tell her anything. I think it's not the right time.

I know all this feels too random and not connected, but I really need help. I cry for her, many times a day. I want everything to be right and be left with no guilt or regret afterwards.