If you haven't been careful to keep things cool and casual between you, issues of jealousy, emotional manipulation, possessiveness and control may have become major problems in this relationship. Your partner provokes an intense response in you, which felt amazing at first. Your sexual attraction to them is overwhelming, and you feel transformed by your intimate experiences together, as if you've finally found The One.
But after a while, you began to affect each other's moods too much; when one of you is down, you both feel out of sorts. If you need some alone time, for whatever reason, your partner feels intensely insecure and abandoned, and they respond by trying to keep you with them by any emotional means necessary -- manipulation and passive-aggression are definitely possibilities. If I can just control my lover into sticking around, your partner thinks, and meeting all my needs whenever I want them to, I'll feel so much better! This is rarely true, though. Dominating another person never brings real satisfaction for either partner. Your individual needs for connection and love could keep you locked into this pattern for quite some time, unless you can find a way to communicate about all these big, overwhelming needs -- and figure out how to meet your own needs so you can come to each other free and clear of emotional baggage.