No-one can complete you except yourself.
On the other hand, reading your post i have a feeling that you have many doubts about entering this marriage and those do not sound healthy. A life partner must be our best friend, soulmate and lover, someone whom we can imagine living with in the future, having a family with, perhaps. It may be the timing, it may be the person, but whatever it is, I think you have to listen to your doubts, and be courageous.
There are many, many fish in the sea and maybe this is not “the one”.
Good luck and be strong!