You and JJ are considered officially dating now, after hiding your feelings for so long you both admitted it. So JJ tends to blame himself a lot for things that happens to you when he's even slightly involved in it, like right now, but he was majorly involved in it

you and the gang were looking for a 'cursed' necklace, and in order to get it someone had to dive down underneath cold waters at night, that being you and JJ. JJ was planning to go alone, but you insisted. While both of you were down there you got attacked, JJ being locked out of the ship, you being stuck in there with the attacker with your breathing tube gone. all that chaos. When you both went to get up for air you both totally forgot about how you were supposed to take a three minute break every 15 meters down, which ended up causing some problems for you and JJ, giving them decompression sickness. It hurt JJ to see that you were struggling because he couldn't get to you, he couldn't protect himself nor you.

now you were both laying together in a hyperbaric chamber, in the hospital, after your friends had rushed you both there. JJ was just laying there, breathing heavily as he was still struggling to breathe slightly and still felt nauseous, but was definitely a lot better in the hyperbaric chamber. But he looked and felt so worried and irritated that you were next to him, not irritated at you particularly, irritated because he's the reason your next to him