A few factors here come into play here.. how are you putting it down?
Second what brand of flooring do you have?
Sometimes, some of the cheaper brands of prefinished floors are not milled correctly and will have gaps.
If you are glueing it down, then you can strap it with some laminate straps to try to bring it more together.
If you are nailing it, are the nails going all the way into the groove?
A way to tell.. dry fit several planks together and see if they are milled right. If they come together smoothly, then its your installation.
Check back with some of the answers.. and we will see if we can help.