
If you've been chopping and changing methods then you are unlikely to have made progress - you need to be consistent. An issue like this can take time to show improvement once the right approach is in place, so you have to perservere with whatever you do. And I agree, you'd be best getting a behaviourist in to observe the behaviour and advise appropriately (not someone who talks about dominance/being pack leader, or anyone who uses punishment of any kind).
In the meantime, have a look here:
http://careforreactivedogs.com/