Getting closure with ex? M 15 F 15

Do you guys support messaging your ex to get 'closure'?

For context: My gf(15f) and I(15m) have been dating for around 7 months. We're high schoolers and I thought we were very close. I had liked her for around a year but never dated her before because she seemed like the type that don't date. So I instead dated this other girl. She and I were together for a year but we broke up because she turned out to be lesbian.

Then a few months later I started dating my now gf because we had grown close due to classes and she confessed to me. She's a scary girl and I'm afraid of making her mad. We don't go out because her parents don't approve of her dating and they also don't let her go out with friends or cousins. So we just talk on text and mostly at school. My parents are aware though because we both have good grades.

Two weeks ago I was feeling helpless in my daily life so I decided to message my ex to get closure because I've been thinking of her for the past 10 months. I don't think I fully got over her. I thought it would bring me some relief and understanding to talk to her. It didn't.

A few days ago I messaged my gf and told her about this. She didn't say anything cruel but she did say that I should of atleast told her beforehand. I don't usually tell her my problems because I'm a reserved guy and I don't want to make her mad. I don't want to lose her. Once we were using TikTok filters and one came up that said 'I'm not fully over my ex', not sure if you've seen those before. I lied and said nah I'm over it. Im also very bad at emotional things such as expressing myself or understanding relationships.

Now she's angry that during the entirety of our relationship I didn't tell her I never truly got over my ex and that I chose to message my ex before talking to her about what is worrying me. She said if I had told her from the start then she would of broken up with me back then so I could figure myself out. But now she feels attached to me.

She's got this guy best friend who's like an elder brother to her and someone she knows longer than she's known me. Around 3 years. I feel quite jealous when I see her messaging him although he does like me alot and he warned me from the start that if I hurt her he'll get his friends to beat me up. He's got these big ass friends in their last 20s for some reason. And he's never made an attempt on her. He's someone she trusts alot because she doesn't really have any friends besides me and him. So I don't know why I feel jealous of him.

She said he's mad at me because I deflect attempts of trying to talk to me one on one and i keep my emotions bottled up to the point that she's left scrambling on ways to help me especially when it's the weekends and she says she can't judge my tone through my texts. I don't knows how to talk to her and I'm scared of being alone. She says she feels hurt that I don't usually talk to her about my feelings and instead I ask my female friends but she does understand that they've known me longer. I think she feels like she can't help me but wants to.

Let me know what you guys think because I'm afraid of losing her and I know she's the type of girl who thinks very logically and yet considers the other person's perspective during arguments. I don't know what I'll do if she leaves me but I don't really do emotional stuff and prefer to keep it hidden.

Thing is that my previous relationship was my first proper relationship so I'm still attached to it.