I'm new to chastity, and today (just as my keyholder started a 3 day lock lol) I decided to try the 51mm ring that came with my cage instead of the 55mm ring. Although I'm normally fine, when I get an erection, my testicles (mostly right testicle for some reason) start hurting. The pain feels similar to blueballs and gets worse the harder I get. The skin also gets darker, becoming fairly purple after a short while. I think it might have to do with the ring being pushed forward when I get erect. Is this normal, or is it dangerous? Is this something I can fix with positioning, or is a 51 mm ring too small? When measuring ring size with a rope I was able to just barely get up to the first knuckle of my index finger under the rope with some working as low as 48.5 mm. 48.5 felt tight but comfortable to me when measuring, no pain after 10 minutes. . When not hard, my testicles feel fine, although after being hard for a while my right testicle hurts a small amount and hurts to touch.