Hay should make up to 80% of the daily food intake, veg about 10% and pellets (don't use muesli/dry mix) only 5%. So please don't panic; it could be that you are simply far too generous with the veg! Your boy is perfectly fine and as he is running an popcorning, a very energetic and happy little one at that!
The food amounts of a balanced diet:
- unlimited hay (timothy or meadow/orchard hay)
- ca. 50g/2 oz of mixed veg, including one high vitamin C veg or fresh herb daily, like a slice of sweet pepper of any colour, a floret or chunk of stem of broccoli or a sprig of coriander/cilantro, parsley, dill, mint or basil
- unlimited pellets until the first quick weekly growth rate is slowing down between 4-6 months old, then very gradually reduced to the half to handful that fully grown guinea pigs over 12-15 months need.
In the longer term, you may want to find him same sex company. Piggies are not wired to live on their own, and you will enjoy the vocal, lively interaction that is making piggies so unique even more! You will find that there is nothing as motivational as the "I want what you have" when it comes to guinea pigs! However, please do your research first before going out to buy another baby boy in order to avoid avoidable problems; you can find a lot of information on this forum.
https://www.theguineapigforum.co.uk/threads/faq-companionship.37654/