Hi and welcome!
Can you please post a picture of what you mean with 'very male'? The testicles descend between around 3/4-6 months of age.
If your boy is an ex-breeder piggy, then you have to be aware that they often tell you the wrong age to put you off breeding their piggies.
My little Nye was supposed to be a year old when in fact his testicles were only starting to descend and he was most decidedly just a baby on the verge of teenagehood...
Here is our sexing guide, which contains pictures of baby boars, boars with descending and boars with fully descended testicles and adult neutered boars:
Sexing Guide
PS: Please consider giving your boy a companion; ideally one that he can choose for himself at a rescue under expert supervision for a stable bond. guinea pigs are group animals and not wired to live as singles. Sadly Switzerland is still the only country where it is illegal to own or sell any group species as singles since 2004 - including explicitly guinea pigs. If you keep single piggies, then the whole responsibility for round the clock companionship and stimulation rests fully for you for every day of the 5-7 years of an average healthy life span. Your piggy's needs never change, whether you are busy or not; and they don't simply go away when it is inconvenient for you.
Companionship
Single Guinea Pigs - Challenges and Responsibilities
A Comprehensive Guide to Guinea Pig Boars (including information on the various ages, pairing up and specific boar needs)
Recommended Guinea Pig Rescues