verification problems on time machine

Hi, Help!

I have had over the last 2 years or so, a message that says time machine has a problem with verification and needs to start a new backup. No problems at all so far.. except now, it has been on the first back up for several days, has consumed 350GB of the disk, and still tells me it is working on first back to complete. The thing is my disk on the Mac Pro is SSD 512GB and I use 216 of it. So it went way past the first backup. seems like its stuck in a loop. also when it is backing up, it can never catch up to the total, that total keeps getting bigger.

so if it says I have 60.5 GB to back up, it increases real-time as it backs up, and eventually, the gap between "backed up and left to back up, gets big.

Can someone help me here, please?!!!

Thank you

Alberto