1. It’s not abnormal to not cry often. I have met many people who have gone decades without crying—(at least, the crying sense in which your post is about. Everyone lacrimates, or produces tears.)
2. It does not make you a wimp for wanting to cry. It peeves me to no end when people view crying as a sign of weakness. Crying can often be an act of release.
Don’t fret about not being able to cry right now. I went a few years without crying (which is bizarre since I tend to cry quite often), but when I did it felt as though those years of feeling were leaving my system. It felt good. In the mean time, there are other ways you can channel your emotions. You’ll likely cry eventually, but there are other ways to express your emotions.
I don’t know whether this will help you, but in my drama class our teacher taught us a trick to cry on cue: think of the happiest moment in your life, every little detail. It has worked for me before.