Is this a new or older laptop? If new, then it may just be how it is. You can always consider exchanging it to see if it is just that particular device. If it is under warranty, then you can have it looked at by the manufacturer (if not completely new).
If it is an older device, it could be the touch pad is just getting worn out and may need replacing.
Without having it looked at, there is no way to tell for certain. However, since you said a mouse doesn't have this issue, then the above are the best options. That or keep using the mouse.