Why does my Poodle have scabs, loss of appetite, pain when picked up?

[BriRose23]

I am just really worried about my boy, he is a poodle cross and is almost 8 years old.  Lately, he has been reluctant to eat very much, less than a cup of food a day. As well as his bowl movements are very inconsistent, a few days he will have lots of trouble pooping and then a few days later he'll have super soft poop.  He has also gotten the random scabs all over his neck/head/upper back area that seem to just want to stay there.  Now, I have always picked him up the same way his entire life and today all of sudden he started whining when I did, which concerned me to the point of coming here for answers.  Hes reluctant to move sometimes (not all the time, he still loves to play with his sister, and do tricks for treats). Side note: he has super bad breath haha dont know if that matters but he hasnt always, maybe i just need to brush his teeth more