Has my BF cheated?

Please help me. Thoughts on what has happened? Should I assume the worst? Very, very worried.

Background: My BF (Fiance actually) was invited to attend the Bday drinks for one of his female sports friends, who he has played team sports with for some years. He has joked in the past that some of the girls from his sports team have crushes on him, and to be honest I'm not too sure how up-front his is with his team-mates about the fact that he is already in a relationship (we all need a little ego boost I guess from time to time!). He has specifically joked in the past that this girl is one that "I need to watch out for", so I'm pretty sure she has been a bit sweet on him. My BF was undecided about whether we would attend her Bday drinks or not, and he only told me on the night that we wouldn't go as none of his other sports team mates would be attending, so we didn't go.

I have since seen the following correspondence between my BF and the lady in metion (who is single), and am feeling quite concerned. Would be very grateful to hear your views on what this all means.

I am wondering what "happened" - did she confess her feelings for him or try to kiss him and now feels embarassed...or has there been a recent more serious cheating incident?

And before you all say "just go and talk to your Fiance about this" and I must reply to say that this is very serious stuff and I am trying to cope and to make some sense of this myself first.

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1) Msg from my BF to female sports mate (day before her bday drinks):

[Dear female friend], was going to call but taking easier way out by emailing.

I have been engaged since November last year. I thought [sports] people knew - [mutual sports friend A] and [mutual sports friend B] did so I figured that meant everyone would then know.

I would like to come to your birthday drinks but [GF] is likely to want to come. Let me know me whether this would still be appropriate.

I would say happy birthday but I don't know the exact date so it may be jumping the gun to say it today.

Love [my BF]

2) Msg from my BF to female sports mate (on day of her bday drinks):

Not read my emails as at [sport]. Ur decision on tonite?

3) Msg from female sports mate to my BF (on day of her bday drinks):

Don�t think it wld be a good idea, not really fair to ask, what happened wouldn�t have if I knew you were engaged. Will see you at [sport] soon.

3) Msg from female sports mate to my BF (midnight post her party):

I am sorry about my text earllier, my friend told me to text that, but honestly you and [GF] is really something I didn't need to deal with tonight, even if it isn't my birthday until next week..... you really have no idea what has been happenning with me recently and out of everyone, other than alex, I thought you would be the one person I could talk to, but now all I think that you think of me is the slut that [mutual friend A] makes out I am, which whether you find suprusing or not is not the truth. I am usually quite fussy. I don't want things to be awkward, and next time I see you I will probably just carry on as though nothing happened, but seriously, do you think so little of me that any one who rocks up in a cab I would let stay over ......?

3) Msg from female sports mate to my BF (next morning after her party):

Second time lucky...sorry about late night email, speak without thinking and say things I shouldn't after a few. Suffering with hangover from hell today, ran out of time to fit dinner in before friends came over yesterday, big error. Was for the best you didn't come last night though. No other [sports friends] made it either.
See you at [sport] soon.

Well, as though the series of emails didn't mention directly their acts, but they can be easily deduced by the way they discussed whether or not it is appropriate to have you, his fiance, to go to a friend's birthday (everyone is allowed to bring their significant others, btw), and with all the "Love", "what happened wouldn't have if I knew you were engaged", "you think of me is the slut", "any one who rocks up in a cab I would let stay over ......?" and so on. A girl who "speak[s] without thinking and say[s] things [she] shouldn't after a few" has great potentials for doing other things she would regret. Therefore, I'd say yes, he's cheated and that they've slept together, at least on one occasion. I would talk to him about this, get things straighten out, consider all your options and if you could live with this or not. But after all, the decision is your. Good luck and sorry this happened to you :(

Why do you have three 3's? . . anyways

1) Text is very formal, he mentioned he was engaged and that you might come. He did end it with 'love' and that could be bad . . . but personally, I end some responces to my platonic female friends like 'love'

3a) "what happened wouldn't have if I knew you were engaged."

Why would she say that? That's definite 'red flag'

3b) "you and [GF] is really something I didn't need to deal with tonight"
and
"next time I see you I will probably just carry on as though nothing happened"

Well she's obviously trying to hide or forget something

==> Doesn't sound good