I think I may still have feelings for someone from my past
How did your feelings for this person come up?
I'm not ready to talk about this right now, as I don't want to lose these memories.
Having old feelings for people come up is natural, but holding on to people when they are gone isn't healthy. Allow yourself some time to treasure those happy memories, and then move on.
Why should I move on?
As you say, this is someone from your past, so it is unlikely that he or she has feelings for you in return.  Since this other person has probably moved on to other things in life, it would be best for you to do the same.  Pining over them will probably just cause you more disappointment later.