You titled your letter to me, 'To Love or Not to Love' and this is the real question for you. You are no different from anyone else. We all have mixed feelings about being too close to others. For some of us the mixed feelings are so strong that they actually prevent a relationship from existing.
Your difficulty with closeness takes the form of cringing when your girl enters your space. The most common reason why one cringes when a lover or spouse enters his/her space is because that person was raised by an overly intrusive, smothering or controlling parent. When your lover comes at you, your unconscious sees your mother or father getting in your face. When you come to your senses, you feel guilty and then you try to make it up to her, but the damage is done. She feels rejected.
Let's go a step farther and consider the fact that many people who have been raised by controlling parents are hypersensitive to being controlled or manipulated (since you received so much of this type of treatment as a kid). Stay with me now. When your girlfriend comes'at' you, you may sense that she wants something from you, like she is feeling needy and is giving to you in order to get something back for herself. Because you are hypersensitive to being controlled and manipulated, you would read the need behind her giving and feel instantly turned off.
Your girlfriend can help you with this aspect of the problem by making sure that she is clear when she approaches you. If she wants something for herself she should preface her approach with a request. Then you won't feel tricked or manipulated into giving. If she comes to give you a kiss without a preface, you can know that there are no hidden agendas. She is just giving you a 'free' gift and knowing that there are no strings attached should make you feel freer to receive her approach. You might also work together on'knocking' before you enter each other 's space.
In other words, before she comes up to you to talk or smother you in kisses, she might ask whether you are busy. A person who grew up with an invasive parent who never respected his/her space especially needs his private space to be respected. If she knocks before entering your emotional space, you will actually be healing your childhood wound. Over time, closeness will feel like a joy rather than an invasion. You will know that you are fully healed when you don't cringe when she comes close.