WOW! Thanks for all the info ladies. And again, I apologize for the delay...Collin has been "after" me to get a J O B, and I really do need one... so I have been super busy with that, as well as the computer probs and recent ex-landlord probs (UURRGGHH!!!! Angry face!!)
Anyway, Duncan went to the vet on Monday. The vet seems to think his behavior is a "prior leg injury" although I have no idea how that would happen without my noticing...Seriously, he is never without me...We have no yard...we walk on measured leashes everywhere...
Whatever, I am never happy with new vets...I never think that they do enough as they feel they have no "vested interest" in the animal as we are not from here....It really bothers me... I should speak up more too so I can blame myself also...
The vet did take blood however. But we did not do the X-Rays. Honestly, $$ is tight since I am not working and I told him to wait on those for the results of the test. We walked for about 1 1/2 miles tonight, no limping noticed....(Funny story: I took the "shortcut" over and over again in case he looked umcomfortable or started limping and we were far from home...Well, these people were having a garage sale and saw us walk by 3 times! They must have thought I was interested in something they had for sale! I felt stupid but....)
So that is where we are....

Dragondawg, you have lots of good info...We are from NY and Lyme is very rare where we are from but we did live in NJ for 6 months and apparently, it is common there...who knew? Now, in PA, it's like an epidemic...I think there are more deer here than people!
Duncan has been eating fine lately. BUT, right after I got him home from the kennel in Jersey back in May, he DIDN'T eat for a few days, had a fever and slept a TON. I just thought that it was because he was exhausted from the kennel and the stress....Maybe it was...I DO NOT want him to have Lyme disease but I also don't want him to have some problem that can't be fixed.... And Lyme can be... so I guess that is the best of the options...besides just a leg sprain...(fingers crossed!)
RE: the aggression: He would probably LOVE to play with other dogs. BUT I can't take the chance....He bit another dog in the eye months ago and since then, I just can't let him around other dogs....I think it makes him MORE aggressive to keep him away if anything..but what can I do???? I can't take the chance of another dog getting hurt you know?
So anyway....let's hope it's his mother's paranoia.... Thanks everyone!!