Who is wrong here?

So, a lot of things need to be said. I live in Ireland and I came to visit my girlfriend. We talked every morning and night, sometimes during the day if we both had time and I was never told she lives with a bunch of guys. So, I had planned on proposing to her when I came (and I did). The day after (yesterday) I had noticed she ad gained some weight (I just didn't think anything about it). Today she decided to tell me she's pregnant The thing is she said she's a few months in, but I wasn't here when she said she got pregnant. I now think she's cheating on me and when I brought it up she started shouting and crying telling me I should be thinking of her like that (but it's the only way).
Another thing is that lately she gets mad over nothing and has the nerves of blaming it on me (when I did absolutely nothing and it's her being in the wrong) and she's been threatening to kill herself and it's kinda starting to piss me off.
And last, she had the AUDACITY to tell people that I'm grooming her. She really says that I'm making her do things and then saying she's begging me to stay with her. I just think she's in this relationship for attention. What should I do?
Who is wrong here?
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