It is completely normal to have one larger testicle and one smaller testicle. As a result, one generally hangs lower than the other one. So don't worry about that. As for the pain, it could be anything. Pain is a sign that something is wrong, so if it is a consistent pain, i'd go see a doctor!
i have been having testicle pains for the past year now. They first treated for epyditimitis and it felt better. However, it has gone and come back many times since. It got so bad one time i went to the hospital and i had exploritory surgery and he glued them n place. Two days before going to the hospital i had rectal pains and it felt wierd around that area. The surgery has been over for awhile now and i still have pain in my testicle. I also have random stomach pains, rectal pains and it still feels like something is wrong with my rectum. The doctors can not figure it out and i have had numerous ct scans and blood test and std checks. Everything comes out to be normal. I am getting very sick now and feeling worse can some please tell me if they have had anything like this and have been fixed or have advise.