Worried about my boyfriends health!!

So me and my boyfriend went to town on Monday, today is Thursday, we had gotten out the truck to go eat and when we got to the restaurant he used the restroom, he came back and then told me that it was harder for him to breath and he felt like he was going to pass out se we went to sit and take a break. Today he told me he felt like that again at work. He’s going to see a doctor Saturday but I’m so worried! I know y’all aren’t doctors but does anyone have any clue what it could be or has this happened to any of y’all before?? I’m just so stressed and worried!! He just texted me as I’m typing this and told me he has a “heart murmur” is that really bad? 😕😕