Pitty's right and @ 1.5g of protein you need 292.5g (1170 cals) 3500 cals may be too much for you right now, but I'm not sure. If your intensity is high then you might burn it off quick. Only one way to find out. But honestly I'm 230lbs and taking less then 2800 cals, but everyone is different.
How much fat/carbs are you taking in ?I'm assuming most of your calories are coming from carbs/fat since 120g of protein is only 480cals then you must be getting 3000 cals from other sources. Unless that 3500 is just an estimate.
Maybe get set up with
www.fitday.com and record everything you eat for a few days.
Hybrid Mode