Puppy troubles?

So my roommate got a puppy back in September, a male chocolate lab/Australian shepherd mix. Nearly every time I sit down, he wants to sit with me, which is fine. Until he starts biting me and not gently. I tell him to get down, push him off of me, tell him "No" very firmly, etc. He just gets more aggressive about it. What can I do to get him to stop? I don't have access to dog trainers in my area, so that isn't an option. It's to the point where I don't even want to be around him even though I love him, he's just way too rough on me. He only does it to me, not my boyfriend or roommate. I'm out of ideas. He has tons of toys, gets to play outside a ton and we play with him all the time. There's no reason for him to act this way towards me.