Boyfriend advice

Ok so, I'm just gonna vent real quick and hopefully get advice. So my boyfriend is a MAJOR hypochondriac. We've been dating for two years. The past year of our relationship every single day he thinks he is dying, I'm truly not exaggerating. He continually thinks he is having a heart attack. I constantly have to repeat it's your anxiety, it's anxiety. But he constantly says "no, I know it's not" he's been to multiple doctors and cardiologists and they've confirmed nothing is wrong, now he is convinced that the doctors were wrong and the test wasn't accurate. I'm starting to lose my patience. I love him to death but EVERY day of hearing that he thinks he is dying is becoming so obnoxious. I truly believe it's anxiety, because he's been diagnosed with it and refuses to take his medication cause he thinks if he takes it his heart will stop in his sleep. Y'all I truly don't know what to do, I'm really losing my mind in all this. Anyone have advice on what I should do? I want him to get better for the sake of our relationship. It's starting to put a toll on our relationship now. Today it was our anniversary and he thought he was going to die during our movie in the theatre. While I was having this great time, watching this movie my boyfriend nudges me saying we need to go cause he's having a heart attack. Which he wasnt. Theirs been multiple times where he's spent hours in the ER when we've had plans because he thought he was dying only to find out yet again he's in good health. He's spent hours on google trying to diagnose himself (which I'll admit I've done) but he begins truly believing he has whatever it may be to a extreme. He's becoming obsessed over the idea that he's dying. I just need guidance and some words of wisdom. Please HELP