My bofriend claims hes never been suicidal but lately he’s been acing like he is and it scares me alot
He cries very easily now and gets scared over little things (like me getting upset at him for something very small)
He wants to get help but he refuses to go to a doctor or take medication because he says hes scared to get addicted like his dad did
He says he’s useless and how he wants to harm himself
And how im his one of the only reasons to live
And it really scares and worries me but I dont know how to help him
I feel like such a horrible girlfriend
Im not good with this type of thing
I feel so useless I dont know how to help
(Screenshots are from this morning)

He may not have been suicidal before, or maybe he just didn't realize he was. (I didn't realize it myself until I was making plans.) But obviously he's suicidal now, so let's focus on that.

I think you should convince him to tell someone. If you're in middle/high school then talk to a trustworthy counselor or teacher. If you're in college then go to student mental health services.

Therapy may not include medication. Maybe it'll just be psychotherapy, or behavioral-cognitive therapy, etc - I'm not really sure what the terms are but you get the gist. Psychologists/Therapists also can't force him to be on medication if he doesn't consent to it (in high school I had a friend with bipolar disorder who went to therapy regularly, but after a year she decided she didn't want to be on medication, so they weaned her off it). Your boyfriend can even inform his therapist that he may be genetically predisposed to addiction, so they can take that into consideration if he does ever decide that meds would be the right decision for him.

If you think he's literally on the verge of doing it, you can call the police. (Idk about other countries, but at least in the US, suicide is legally considered a crime so that the cops can enter private property to prevent a crime from being committed.) This might have consequences later on for him (I'm not sure what the rules are about forced hospitalization for suicidal patients) but at least he'll be alive.

If he refuses help but is still showing this sort of behavior then consider telling a counselor/teacher/health services yourself. Again, he'll probably be upset, but you're just one person who's not trained to deal with this sort of thing. For him to say things like "if it wasn't for you, I'd kill myself" is a LOT of pressure, and in worst case scenarios, it'd be abusive if he ever uses that line to manipulate you. (Not saying that he's doing that to you now, but that's where things go with some people.) For both his sake and your own, if it becomes too much for you, you can tell someone else who's more qualified to help him. It's not wrong of you to do so. Like you siad, this is scary stuff.

Also, you're not a horrible girlfriend. You're clearly very worried about him.

I hope that this helped, and I hope even more that things start going well for the two of you. Update us when you can xx