Is this just a spying technique?

My bf is notorious for wanting to go through my phone. In the beginning when I didnt take him serious and I would talk to whoever I wanted within certain limitations of course. If I left it out he would go through it for whatever. I got so tired of him doing I actually left my phone off for quite some time then when I turned it back on I put a lock on it. I have to keep the damn thing on me cause he is so nosey. Im not cheating on him so it irritates me that he does this. Now he's asking me if I want to share his phone plan with him. Is this just a tactic to see everyone Im talking to or a genuinely nice gesture since Im almost 5 months pregnant with our first little girl?