The 'healthy weight range' of a sun conure is generally given as 100-120g. So by that standard, yes, yours would be considered overweight. However, there are many things to take into account. Including your vet. There are two avian vets where I take Skittles and his weight has always been in the 119g-122g. One vet has said hes underweight the other that he is overweight. I disagree with both.
The BEST way to tell if your sunnie is overweight is to take your thumb and index finger and rub down the front breastbone of your sunny. There should be VERY little between the front of the breastbone and the skin/feathers. GENTLY slide your fingers forward (as if rubbing both sides of the breastbone) and see how much 'muscle' shows up. There should be a small, healthy amount of muscle there but not too much. Tip: Do NOT try this while their crop is full. Lastly, Skittles is free-flighted, eats like pig, has only a small amount of muscle on each side and weighs 122g. He's about twice the size of an adult female cockatiel in terms of body frame.