MY dog is about to be five please help with veteranary advise?

my dog is about to be 5 years old. Usually very spunky, spontanious, and energetic. Lately (in the past two weeks) he seems like his joints are hurting him when he gets up (stands up, gets off the couch, goes up or down stairs or jumps on or off a bed). His whole body looks stiff, but if we take him outside he runs around like nothing is wrong. We found a tick on him about a month ago, but it was already out when we found it. It looked infected for a week, but healed up and we can see no signs of it. We also have been under alot of stress in the house.....someone help me..... is it lime diesease or stress or what is wrong with him?????