Decay on teeth, worried about sensitivity

[marymarysue]

I have been feeling more sensitivity on my teeth than usual, and feel like I can move my filling with my tongue. I don't have a back molar, the one at the very back is a grown in wisdom, but the one I am inquiring about is the premolar. I am terrified of extractions, and am so scared that this tooth is having decay or cavities, because the filling on the right side of my mouth is even more sunken in, which is why I have started using this side after the filling. The photos show the before and after, and the circled areas that I notice more browning around and/or feel more sensitivity around.

I don't know what to do. I do everything 'correct' for my dental care, even as far to changing my diet and when I eat, and if these things are not helping, I don't know what to do. I feel like a time bomb just waiting to get all my bottom molars pulled, and i'm not even 23 yet.

 

[Gordon]

1) That's a first molar, not a premolar
2) That's just staining, I can't see any decay in those photos
3) Sensitivity may be because the 2nd molar is missing and a bit of the root surface will become exposed between this molar and the 3rd molar.

 

[marymarysue]

@Gordon Thank you for the correction and your response!