it's honestly different for many people but most signs that i've personally went through and have seen my other friends also go through is oversleeping/undersleeping, weird fluctuations with weight (gaining, losing weight, etc.), lacking interests in hobbies you once loved as well as your friends, negativity or irritation, lacking personal hygiene. again, this is only a few and may or may not apply to you. hope this helps :)

Pretty much yup when you think it's getting worse it's getting well worse. Also if your thinking of attempting suicide that's probably when it's really bad so you should probably catch yourself before you do anything like that. But yah definitely if you know your no longer enjoying things you used to enjoy. It's affecting your job or getting out of bed. You just realize your having way more bad days then good is a indication that it's getting worse.