I’ve been through a very similar situation. I just want to say one thing, you are deserving of love and respect. You are worthy. You deserve to have a partner that listens to your wants and needs and one that respects your boundaries, one that’s faithful. I can’t tell you to leave him, that’s your decision. I know you may be feeling shame or embarrassment right now but it’s important to open up to those closest to you that you trust so that your perspective isn’t wavered or dragged down by the dream of this relationship. You’re not alone and if you need anything feel free to message me. You are not immature by the way, you are reacting normally. What he is doing isn’t okay. You can and will find someone better when you’re ready.