So you have found yourself missing your partner more than usual and aren't sure why. You may be missing them because you are becoming more emotionally attached. Whenever I have started dating someone I know that the more I get to know them the more I want to spend time with them, that because your feelings do get stronger over time.
The feelings tend to get stronger when you have a close relationship where you both share almost everything. When your partner is away from you there are times when you start to feel like a part of you is missing, almost like another half of you is missing. This is an emotional attachment that has quite a lot to do with the chemicals in your brain that is released as you begin to fall in love, it's probably one of the strongest emotions out there.
One of these chemicals is called Dopamine, it's a feeling of euphoria, elated, and attached. This could be one of the reasons why you may go through your highs when they are around both physically and mentally. It's also another reason why you might be getting a little worried when your partner isn't around because you feel like you are missing out on something, or you may start to get jealous that they are around other people and not you. Basically, you are missing them.
This sense of ownership comes as the feelings get stronger over time, it's the same sort of thing when you get attached to a pet, if you notice your pet is giving more attention to someone else you may start to feel left out. It's a natural human reaction when emotionally attached, so long as you don't allow yourself to get too caught up in it and avoid thinking about it as much as possible you won't become too overbearing and clingy towards your partner which we all know is a big turn off.
If anything, take this time to do the things you enjoy that maybe your partner doesn't really want to do.