My boyfriend seems really distant lately and on the weekend we were together he spent most the time we were out messaging on his phone then saying that nothing was wrong... but he was taking to this girl who tells him she'll kill herself if he stops talking to her and stuff and now he has invited her to his party after telling me he didn't want her to come because she might start drama. He's also going to his friends party this weekend and she is gonna be there and he told me not to worry he won't do anything stupid but she has a hold over him because he doesn't want her to kill herself like she says she will. I'm just worried something will happen between them or has already considering he is horrible at certain things... but was somehow good on the weekend?

More likely he’s cheating. So just dump him before he does wrong or has already done.

Rather than dumping him outward, i'd advice seeing how things escalate and just calmly talking with him about it. There's a good chance he just wanted to help this girl. Wait a bit, find a good moment to seriously talk to him about what's worrying you and PLEASE be clear about what you mean.

Every time I see something like this I think about how important communication is. Tell him his contact with this girl is making you uncomfortable because of X, Y, and Z. Like a previous commenter said he could very well have the other girl's best health in mind and there could be no cheating going on, but if he has YOUR best interest in mind he should be comfortable and open to talk through the issues with you about this girl.

Thanks for replying. I will speak with him the next time we see each other in person. I think maybe my doubts are coming from the fact that he had been on dates with that girl before we met and even has been asked by a work colleague if he wants to be fwb. Also that very few of his friends actually approve of our relationship one going so far as to say how I'm ugly and he could do so much better...