aitah because my ex bf accused me of dating a girl while we were dating?

so this story was a little bit ago but this has been lingering on my mind. One night we were on a phone call for a like an hour but I had to help my mom cook dinner because we were having a get together and I was just chilling in my sisters room for a little bit, and I left my phone in there... and it was on.

my sister got on my phone and started to text my bf. saying that I am a lesbian and that i've been dating a girl. which i haven't. than his online friend fuck ass rumi started to yap her mouth but she said that im an asshole for cheating on my bf. she said more but i'm not going to repeat it.

than came back to my sister crying saying "im so sorry" and "I didn't mean to I was trying to be funny" I than took the phone and started to hug her trying to comfort her than i said " what happened honey" then she started to explain what happened .

I was trying to be as calm as i could but i couldnt shake the fact of what could've happened. I than grabbed the phone from the edge of the bed and asked what happened . she said that she was trying to prank my bf. she had been a little brat sometimes but this was too far, she seemed very shook, and she didn't want me to see what happened.

but than she showed the messages and my bf seemed very upset and he said and i quote "what did i do to deserve this'' i was so devastated to see that my bf was starting to believe the lies my sister was feeding him.

I felt so bad that I had to send my sister out of her room. I started to text my bf and tried to explain what happened and he started to argue with me starting to say I don't want to talk right now and just leave me alone. I tried, I really tried. I didn't want the relationship to end.

I then tried to call him and say that wasn't me, and he chose not to believe me he didnt pick up. i tried to explain to my sister that "its ok you were trying to be funny but you took it a little too far" I then called again and said that that wasn't me I was helping me mom cook. and then he said "I dont need an explanation, I already know enough." he than hung up. wtf? I was now pissed. not mad at lilly but it was half her fault.

I was now spam texting him, saying that wtf does that mean. and does that mean you believe me now? He said he needs a break, and we all know that means after a week or two that we are going to break up. I didn't want to be hurt any more and I thought it was dumb just to take a break, so I ended it there.

I said "If you wanna take a break than we cant date. I think that its dumb that you need to take a break from your gf of 2 years for something that didn't really happen. (take a break yea you) then a friend.... she said that she had feelings for me and said that she heard that me and my bf broke up. nothing else happened because i tried him asking him out again ill give you an update when somin happens.