I am so, so sorry you are feeling so hopeless. You are only 22! You have plenty of time to find the person who is right for you.
It may be a small comfort but I get letters like yours all the time — sometimes from kids as young as 12. In the U.S., we seem to be living in a culture that suggests that if you haven’t found true love (and good sex) by your teens, there is something wrong with you. As a result, young people are jumping into commitment – and sex – in order to feel “normal” even when they aren’t ready for it.
Contrary to what you may have seen on TV and in the movies, what is really normal is moving gradually from group activities to a number of short-term and shallow relationships to, after many years, a committed relationship. In fact, people who marry in their late 20’s and early 30’s are more likely to have marriages that last. Why? Because these people have taken the time to mature and to figure out just what kind of person is the right fit for them. What you are doing is not only normative but is very important.
You have many fine attributes. I see no reason for you to decide that you are unloveable. But there may be some things about the clinginess and impatience that you described that are off-putting. I suggest you give yourself the gift of a few counseling sessions to talk that over with a qualified counselor. There may be a few things you can change that will make others feel more comfortable around you.
I wish you well.