Jealousy, emotional manipulation, possessiveness and control are likely major components of this relationship if you both weren't careful to sort out your feelings from the start. You've been stirring up intense feelings in your partner from the very beginning. Your sexual attraction to them may also be overwhelming, and you feel transformed by your intimate experiences together.
Your emotional lives are closely linked, almost without your having noticed when they merged. And that's when the trouble started. Any separations could leave you feeling intensely insecure, even abandoned, but if that happens, it might have more to do with the kind of dependency your lover has worked hard to create than with anything really to do with you. In fact, they might be the one that really feels insecure and bereft when you display your independence. This kind of emotional extreme can lead the best of us toward urges of possession and manipulation, although dominating each other never brings real satisfaction for either partner. But your partner likely tries it anyway, because your relationship feels so vital to their well-being. Your individual needs for connection and love could be keeping you locked into this pattern, unless you can find a way to examine your emotional life and figure out why you've made the choices you have in your love life. It could be that you feel an overwhelming need for companionship, and that has led you into this controlling, emotionally twisted situation. You both have to learn to stand on your own two feet if you don't want to wear each other out completely.