Teeth are going more and more Transparent and feel so thin and sensitive! Help!!!

My front teeth have been becoming more and more transparent/translucent/clear, and I feel they are getting weaker and thinner! I had Laser Zoom whitening done 4 years ago, and have been using Pro-Namel toothpaste since then. It isn't working. These past couple of days, they have been feeling like I just got them whitened today! Even though I haven't used any whitening product since then.

I feel like the pain is shooting up into my gums, especially my front top two teeth. The two top and bottom teeth are starting to chip around the edges, and I'm scared they are just going to break off!!

Veneers could protect them but I can't afford $1000 per veneer.

Please if you can help me, is there anything I could do to prevent it from worsening, and to restore the white and thickness?

Thank you