My girlfriend doesn't show affection like when we were together before I need advice

Talk with her about this, you're in a relationship , ''together'', so talk with her, see what's bothering her .

As far as I can tell, the only way to understand girls is to ask them upfront :S.

Relationships can go cold for a lot of reasons - boredom, time constraints, family pressures, etc. The one thing you can do is inject some fun and adventure back into your life together. Avoid going to the same old places all the time. Look for some new sources of entertainment like concerts, dancing, sports games, flea markets... stuff like that. It is worth a try. Maybe a change of scenery will improve your chemistry.

As far as I can tell, the only way to understand girls is to ask them upfront :S.

Yes, but ask them in private, you might be getting the better answer there.