Well it's good to see you again. Welcome back.
I don't know how long you've been away for, but I think you've done a great job at recognizing that you
need to come back after only a 15 lb re-gain.
Now that you've recommitted, you'll have those 15 lbs off before you know it. You'll be in a great groove (frame of mind) and will continue on and lose plenty more as well.
Oh and I'd lose that shame and guilt. What good are they? Things like this happen. Move on. What's done is done. Forget yesterday and focus on TODAY. What can you do TODAY to get where you want to be?
I look forward to hearing of your progress.