That's not lag, that's HDD/system hitching.
I would hazard a guess that your system is underpowered. Especially since you are playing on a Laptop. Is your CPU even dual-core or is it a single-core?
The loading times are likely because you are using a slow laptop HDD and they typically don't even run at 7200RPM.
Try turning down your graphics options to the bare minimum settings and see how much your performance improves. Then from there slowly tweak one setting up at a time until you get something you think looks good enough while still performing decent enough.
