How do I tell whether I need another advisor?
He constantly forgets meeting. 


That's normal (and perhaps a good sign). You need to take control and establish a procedure to ensure meetings take place. (It's perhaps a good sign, since it suggests your supervisor is busy.


  I feel he is not able to suggest me good references or offer help. 


For good references, that's probably normal: You've been conducting research for over one year and your knowledge of the research domain now exceeds your supervisor's, hence, you are more familiar with the good references. An exception arises if the good references are unspecialised, but that doesn't seem to be the case, since "he is giving me something that he is not very familiar with."

For offer help, you'll need to provide more context. As it stands, I cannot judge whether the degree of help is normal.


  once I...could not find [what] he suggested me, and it turned out he remembered it wrong


That's normal, he's human.


  I guess one direct reason why I am posting this is I have not made any progress reading one paper (not even doing a problem) since 3 or 4 months ago. 


This is perhaps your real problem. 


  I could not answer my advisor's questions about the paper perfectly as
  he wants and he would not let me move on. 


That's good; you probably need to understand the material before you move on.


  I do not really see the meaning of doing it 


Why not?


  and he could not give any suggestions, 


What suggestions do you expect?


  and lost motivations, 


See elsewhere on this forum for questions regarding lost motivation.