having trouble with soon to be step son

has anybody had problems with there step kids doing homework, i have my boyfriends son and helps him with math homework but he dont want to do it. i dont feel like he really gets it, i dont know what to do. i want to help out as much i can, there is only so much i can do due to being almost 36 weeks pregnant.. what is he going to do when i have this baby. i am worried. he is only in 6th grade i dont feel like he is going to make it onto the next grade. he has games and computer at our house should we take it away untill he can do better in school or what should we do, i am so confused. not sure what to do? any advise will be appreciated.