So I 18m and my gf 17f have been dating for about 4 months now and I just recently found out about her exes. My gf and I tell each other everything even during the talking stage of our relationship but recently I found out 2/3 of her exes from some mutual friends even though she knows mine. she said it never came up in conversation even though we have talked about exes before, but on our nightly call she told me that she used to date my best friend of 14 yrs in middle school which is a very long time ago but the fact that neither of them told me made me feel some type of way. im normally not a petty person but it made me upset and i went quiet on the phone to think and i cant even look at my. best friend the same. aitah for getting upset?