So just a PSA for minors:
If you feel terrible being around someone and they are emotionally draining you, but you feel obligated to be there for them likely you are being emotionally blackmailed.
"you should send me X to cheer me up"
not normal
"can we call I feel depressed"
the call is just sobbing uncontrollably, but they are magically horny 5 min later
"don't hurt me or I will kill myself" etc etc.
Usually said in less direct ways, but that's the gist.
Just block them they won't do anything, and even if they do it's not your fault. You shouldn't feel obligated to "be there for someone" to your own detriment or feel obligated to do anything sexually with someone.
It's common in more tumblr spaces, and usually it takes the form of "if you expose me I will kill myself" (they never do trust). Most reasonable people understand if they get "exposed" it's due to their own actions and even if it was shitty, it still doesn't warrant emotionally blackmailing someone much younger.
I am friends with many people with BPD and often they do similar things, but it's far less calculated and it's clearly genuine. Some people of bipolar disorder and they "switch", but in neither case are people fine on the public timeline and in other people's DMs, but uncontrollably depressed in yours.
You aren't responsible for anyone's emotional well-being online, much less someone who is 3-15 years older than you so feel free to block them and report them even. You don't need to give them an explanation, if you feel trapped in a situation and you don't want to be in it just block.
You shouldn't be someone's emotional punching bag.