How do I tell whether I need another advisor? I am a second year PhD student in math. I recently feel miserable working with my current advisor so I am considering switching advisor or adding a second advisor. 

A few problems I can think of at this moment which make me want another advisor include:


He constantly forgets meeting. For example, I schedule it with him on Wednesday. He would probably forget it on Friday. Of course this is minor if I send out a reminder in the morning on the day...
I feel he is not able to suggest me good references or offer help. I am surely not an independent enough student that can work on my own yet. I kept desperately seeking answers online, asking everywhere, and probably spamming the authors who wrote the papers... This is probably the right way of doing research, but I doubt whether I could speed up my progress a bit if I could get more help from my advisor.
I guess one reason also for the last paragraph is he is giving me something that he is not very familiar with. I believe this is probably the case with most advisors. But once I tried to search for a long time and just could not find an object in the problem that he suggested me, and it turned out he remembered it wrong... I just wish he could be less careless.


I actually kind of transferred following my advisor to this university, so I tried to work with him since I came here, though I actually did not really start working with him in my previous school and came here as a first year student. I always thought seeking for another advisor would again take effort, and the miseries come and go, so I just did not do anything with it.

What I am thinking now is, if everything like the above is normal for a math advisor, then I would like to convince myself and go along with it. My miseries are probably just what I need to bare to do math, but If it is not, I really hope to get more help and support from my advisor for my next a few years in grad school. 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. I could not answer my advisor's questions about the paper perfectly as he wants and he would not let me move on. I do not really see the meaning of doing it and he could not give any suggestions, and I started to hate the math and lost motivations, so I think I definitely want some adjustment, either real or mental.

Thanks in advance for any advice.
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.