Licking himself causing strong smelling discharge (not normal urine smell)

He is 3 years old and we have noticed him doing this periodically...he is crate trained and we keep towels in there...so we know when he is doing this because of the smell...He hasn't done it for awhile but today he was sitting with me and not paying attention the next thing I know he did it and became aggressive when I tried to get him to move because he was licking it....he did this earlier this morning also

He has been fixed since he was 6 months old...we just had to move across country so he has been under a lot of stress...we are living in a suite right now till we close on our house.

Could this just be his way of showing us he is not happy with the change?

Can someone help me???