My 9 year old Chihuahua yelps when I pick him up

[Angeleyez1613]

Hi I have a 9 year old Chihuahua that yelps when picked up or when any kind of movement is made near him.At first I thought it was because he was constipated because he hadn't gone to the bathroom in two days so I gave him pumpkin and he went a tiny bit but not like usual. I'm at a loss because I don't know what is wrong with him. I don't know if it is his stomach or his back legs.He every now and then limps but not all the time. I really need help and any suggestions are really appreciated. I don't have any money to take him to the vet so anything I can do at home to find out what is hurting him and how to treat it is very much appreciated as well.