Help bf with mood swings and snapping

I know he loves me and treats me good when we’re together and cuddling but as soon as i go home something changes he tells me because he doesnt feel a connection over the phone. But i tell him thats our only option for now until we move in together in the future. He seems distant and like he doent care about us or me. He forgets everything when he’s mad. He blames his anger and mood swings and snapping at his mental state he claims he has bipolar but i dont think he does. I feel like its just an excuse for him to act like that with me. I told him if you do have it ill be here for you, but you have to go to the doctors to check it out. But i can say anything and he snaps and claims im being petty when im not, he tells me i dont know how to talk cause he feels i sound petty or angry or sarcastic when im not. And then a couple minutes or hours he says he’s sorry and that he shouldnt be treating me like that and i forgive him .