This. Because it's hard to tell if your chest is really 'soft' since chest muscles are supposed to be soft when they're relaxed, not to mention soft is a subjective word.

Would you mind sharing your chest workouts? Do you think you eat enough protein? To be frank, I don't really see you have a good amount of muscles, of course it could be angle and lighting problem.

Protein as in protein from food sources, not those protein powder. I don't recommend eating them either unless you're a gym freak, but you have to make sure you eat enough protein to let your muscles grow. I believe you have grasped the reason behind the problem you're facing already. Cheers.

Everyone's fat distribution will be slightly different. Your body might store more fats on your chest compared to other people. It's not a big deal TBH since the doctor you met has said your body is normal. Just try to think about people that have low body fat but still have no jawline, it's the same thing except their bodies store fats on their jaws instead of chest.

If you suspect you have mild gyno, you can always try to pinch your areola and check whether its texture is consistent with the texture nearby it or not, if it's not consistent, then there might be a breast tissue, even then it's still not a big deal since it doesn't affect the appearance unlike other cases of gyno.