As your headshot is intended to be an accurate representation of what you look like, one should be careful about the feedback sometimes given by certain individuals. And by that I mean the people that you are most likely to get feedback from first, your family and close personal friends. This does not mean you should invalidate any feedback you receive from family or friends, it just means you should also solicit feedback from people outside of this circle.
Who can you trust? Well, with regards to providing feedback as to whether your headshot actually looks like you, almost anyone who isn't a close friend or relative. But when it comes to judging the effectiveness of your headshots, it's a bit more difficult.
Probably the people who can most accurately assess your headshots are casting directors. However, it is entirely unlikely you have one at your disposal. Probably the next "most qualified" people are professional photographers who have headshots experience, BUT for obvious reasons you'll still need to take what any photographer says about your headshots with a grain of salt. Particularly if they are not positive and especially if it seems the reason they are being critical is simply to get your business. With that said, not every professional photographer has their own agenda.