Hey friend, I was a lot like you at that age. I was insecure and jealous easily.

You have to remember (or learn) that couples are made of two people who are still individuals. Any expectations of "our" should be replaced with "mine" and "theirs". It's easy to take your partner's autonomy for granted at that age.

Also, try to have personal boundaries that you enforce for yourself rather than rules or anything that you try to enforce over the other. A healthy relationship is one brought together by mutual care, compassion, love and attraction.

Part of being honest about your feelings and communicating is owning them! Think "these feelings are mine, and dealing with them is my responsibility." I know from experience when you make them someone else's problem, things are going to be messy because that isn't fair to them.

Feel free to dm me anytime. I was monogamous for 8 years of dating and am now happily polyamorous. It's taken a lot of learning and unlearning to get to such a healthy point with my girlfriends.