Is it normal to still an about an ex?

Yes, after an intial break up, it is normal. If you can transfer to another department, you may want to consider this. Or, you may look for another job. This is why I think it is not a good idea to date co workers or to get overly chummy with co workers. When these realtionships go south, there you are. You still have to work with them. Good Luck!