Got 2 Veneers a month ago and now I'm experiencing a popping on my tooth. What would be causing my teeth to feel loose?

With limited information, my first thought is that the length may be too long and that could be creating additional pressure onto the teeth which could allow increased tooth mobility, not veneer loosening at this time.The steps I typically take are 1) make sure the bite is harmonious especially with "parafunction/bruxism" unconscious habit biting (usually@sleep) 2) marginal polishing 3) marginal thickness 4) biological width (depth) of the gum sulcus.Also, I have seen gums take 3-4 months to improve due to multiple variables.  Just make sure you are not sipping/drinking any soft drinks or any other sugar or acidic containing drinks as this could prolong the redness.

Without seeing you in person, it's difficult to say what the issue may be. If the margins of the veneers are irregular, that may cause plaque to accumulate at the gumline causing the redness. Sometimes people have a reaction to the material or cement used, which can cause redness of the gums. As far as the veneers being loose, if they aren't coming off and 2 different dentists state they aren't loose, I don't know what else it could be. Veneers are bonded to the teeth, so they will typically fall off if the bond fails. They won't just be loose. 

So sorry to hear you are experiencing this.  I will tell you first and foremost we want our teeth to move.  They all have ligaments surrounding them (The periodontal ligament - literally meaning - surrounding the tooth).  This is similar to other ligaments in our body.  If we couldn't wiggle our teeth a little - it would be disastrous when we ever got bumped or bit on something really hard as the teeth would shatter.  So you may be now noticing tooth movement you weren't aware of before considering you weren't focused on these teeth.  The teeth may also be experiencing something called crepitus - that is when you bite down and clench certain teeth move when they shouldn't - this might have happened if the occlusion or your bite was changed at all with the veneers.  Lastly but most unlikely seeing as two docs have checked you out - there may be an air bubble in the cement causing you to sense the proprioception of something not right.  I hope this helps.