Not sure, they could be. If it is a male tree, will it ever bear fruit?

I can't help you there, I'm afraid. Mulberries can have male and female flowers on separate trees or on a single tree.

I agree that male flowers is the most likely explanation. It could have been mislabeled because named mulberry varieties should really be fully female. Still, I have heard about female mulberry trees changing over to male at random. You may have to start over with a new tree or better yet, graft onto this one. Bark grafting would be easy and in a year or so you would gain back the lost growth.

Definitely confirm that this is what is going on though first. Maybe you can post a close-up of the flowers...

That looks nothing like the fruit of Pakistan. Immature fruit starts out white, then as it grows it turns lilac, then purple. However, it always is "plump" looking along its length, like a blackberry, and the fruits of Pakistan are 4 to 5 inches long. That looks unfortunately like a male pollen, which Pakistan does not have, and I agree you probably got a mislabeled tree.
You could graft on to it (I have an overgrafted male I used as an understock) but you will get fruit much faster if you buy a new tree ASAP. Hopefully the place you bought it has a guarantee!!

Carla in Sac

LECooke's has photos of what the young fruit should look like

http://www.lecooke.com/fruit-trees/mulberry-trees.html

Carla in Sac

I found some pictures of male pollen and it match my tree, so looks like I have a male tree. So male tree do not bear fruit at all? This tree really grew fast and now a big tree that can not be taken out. I would have to cut it down. I can look into grafting option.

Pakistan does not have male flowers--you almost certainly have a common street tree mulberry, not a fruiting mulberry, and not Pakistan. If you want fruit, you need a new tree. It may be big now, but it's never going to get any smaller LOL, plus many people are horribly allergic to male mulberry pollen.

Carla in Sac

Got it. This tree is getting out of here. Thank Carla and everyone for your help.