Naturally,one testis will be at higher level than another.The scrotal skin will become tight or loose depending on the climate .
You need not worry about it also.
Regarding the size of the testis,you have to consult a surgeon/urologist
and get it confirmed.
You need to take an Ultrasound scrotum
for exact diagnosis.
if you come back with scan report,i will clarify further
Wish you good health