My fiancé (long but need help)

Let's start this off by me saying I love him. If the only thing you can tell me is to leave then don't respond. This goes to all the women with a bi polar man. Diagnosed by a doctor not just self diagnosed. How do you make sure he takes his meds on time? He will take them like he's supposed to but if he doesn't he will get into a habit of not taking them. He isn't too bad off of them until something happens and ticks him off. He has never and will never hit me. He does get kind of mentally abusive but still is cautious enough with me to where what he says can be forgiven. With everything's his sons mother does he is careful to do things or say thing Infront of his son and if he starts wilding out even after he takes his meds he leaves and comes back with ice cream for him. He's a great father and an amazing partner and I'm glad he is concious of me and even more his 2 year old when he gets set off but I'm just worried if it will change when our daughter gets here. How can I make sure he stays on top of his meds? Everytime I bring it up he gets offended that I may think he will do something but with his illness, you never do know.