It sounds like you are genuinely concerned about the quality of your dating life and whether never being single for very long might mean that you have a personal problem. There are two key things you mentioned that indicate this may be a problem. First, you are wondering if it is healthy to go from being a “couple” to being another “couple” so quickly and so often. Second, you realize that you are sometimes dating people that you don’t even like very much.
Common sense suggests that the whole point of dating is to get to know people you are very interested in, people that you like and to whom you feel attracted. When you find yourself dating just to date or being in a relationship just to be in a relationship, the pleasurable purpose of dating and relationships are basically lost.
In my experience as a therapist, I have found a few common themes in the motivations and psychology of people (women or men) who engage in this pattern. Quite often, this pattern reflects an underlying fear of being alone, a fear of feeling lonely, or not knowing what to do with oneself as a single person. Being liked and being in a relationship is a part of the basis for most people’s self-esteem, but healthy individuals also derive self-esteem from other sources as well. Self-esteem may also come from their own accomplishments, their friends, and their activities and interests apart from a relationship. Deriving all of your self-worth from being part of a couple is based in fear and perhaps not knowing yourself as a person apart from being someone’s girlfriend or significant other.
Another pattern I have noticed is dependency and a lack of confidence in being an independent person. Feeling independent comes fairly naturally to some women, but for many it is an acquired skill. Spending time with women friends that seem to have this quality of independence can help you observe and practice the ways they successfully create an independent self in the world.
Finally, it sounds like your choices have a compulsive quality and that they are often driven by the needs and designs of the person you are dating. If you suddenly find yourself in an unwanted couple relationship, it means you are not steering the relation-“ship”. If you feel that some of these issues apply to you, it would probably be helpful to seek a therapist that can help you sort these things out and develop new more satisfying patterns of dealing with relationships.