Getting married is an important goal not just for you but, most likely, also for the person you are dating. If you are continually getting rejections, it is from another person who also is looking for a relationship.
If you have difficulties when dating one or two people, there is no reason to think much about it. Most people don’t marry the first person they date. Perhaps it is disappointing, but move on and you’ll be fine. However, if things are going to plan and you keep getting turned down, it is vital that you stop and ask “why?”
It may, for example, be to do with the kind of person you are looking for or things a reference is saying about you. It could also have something to do with how you carry yourself during dates, or the things you are saying about yourself. Reflect deeply, request feedback, seek advice.