Whining, trying to bite tail, favouring leg

He could have impacted anal glands- that may explain biting his butt and whimpering, but I'm not sure about favoring his leg.
Let us know what the vet says, and welcome to the boards!!

Welcome to idog itsjill;  The first thing I thought of was impacted anal sacs too, or something in his colon that he is having trouble passing. If his anal sacs are impacted or infected you may see some leakage of fluid from the rectum, or the skin around the rectum may be red and irritated. Please let us know what the vet says. I hope it isn't anything serious.

What does the area look like?  Is it at all swollen or tender?  It's a bit tough to tell without more description.  No lumps or even tiny bite marks?? (almost sounds like a bite of a spider or something that will cause lingering pain) -- and anal gland problems are always a possible but I would have thot you'd have seen scooting or distress before you'd see pain.
 
Kudos that you are getting him right IN to the vet!  And welcome to I-Dog

Thanks everyone.
He's not scooting. I can touch his legs, tail and hind quarters. He licks me when I do that.
I couldn't stand the crying (thank goodness I have no human children).
 I took Buddy for a car ride hoping that would make him happy and distract him. We went and got my guy, and the 3 of us went for a drive, and buddy who usually has heart failure everytime he see's my guy didn't blink an eye.
I haven't seen him pee. I saw him try to cock his leg, but his other was shaking quite a bit so he didn't go.
He reluctanly has eaten a hotdog ( he normally doesn't chew, you know just swallow.....lol) he took his time with it.
He's lying out on my back deck. He's panting quite a bit as well.
Here's my normally happy boy just yesterday.
Thanks for the help everyone Im feeling better already...now Buddy's turn.
 
A 90lb lap dog is enough on a good day, let alone when he is so under the weather.

His picture is adorable!
For me, the panting means that he sure isn't feeling well. 
Did you take him to the vet yet?

  I wonder if he could have a pinched nerve or an irritated disc in his spinal column because of it hurting when he moves his rear legs.

He is beautiful.  I sure hope you get to the bottom of his problem in a hurry and that handsome guy gets to feeling better.

Thanks again all.
The vet was at a bit of a loss. Isn't that great
He drained his anal sacs (there's a thankless job). Everything was all clear. He said they were not bad. I believe he said mildly full.
He checked him over and gave him a clean bill of health.
Also a shot to stop the itch.
Buddy seems a little happier, but not his normal self. Morning walk is just about here, so maybe that will cheer him up.

Hopefully he has a bug that is going away. Or maybe he jumped up or off of something and had a slight injury,,and its feeling better.
Good luck! Let us know.

   Maybe it was something like a spider bite like Callie suggested which would explain why the vet didn't find anything.  Did your vet feel along the back bone to see if it could be a pinched nerve or sore disc? PLease keep us informed; I hope he's back to his old self soon.

Something similar happened to Romeo once,  he could not move, he would try to take a step and would fall to the ground crying and trying to lick his back leg.  Since it happened during our morning walk, I was like a mile and a half from home, had to call my dad and I immediately took him to the emergency vet, she said biten by a bug or spider, gave him a couple of shots, and medication to take home, by the evening though he was feeling much better, but during those couple of hours and while waiting for my father, I was a wreck!  Hope your baby is feeling better.