Help! I don't want to ruin the best thing that has ever happened to me :-(

Hi Everyone, ChrisHamlin1 here.

I was hoping this would be a place for some advice. I have recently entered a relationship with a girl with whom I am very much in love and am already thinking out my future with her despite only being with her not even 3 months at this stage.
During Sexual Intercourse however, I am often finding it difficult to get & maintain an erection and I am very worried this will negatively effect our relationship at this early stage. I am a Diabetic and I am hoping that the issues are simply down to issues related to this as they could be treated medically.

What has prompted me to create this thread however is a persistent nagging question over whether I am bisexual or even homosexual. I have often fantasized about both men & women despite never wanting an actual relationship with men, only women and only ever been intimate with women in the past...but in recent years especially with being single for a long time I have favored fantasizing about men. I have never been intimate with a man as I have stated but recently I have even experimented with crossdressing and found that quite enjoyable and even 'kinky' I would like to find clarity that this is just a private kink/fantasy but I very much want to make sure I can find a way past this and for this to not jeopardize my future with amazing girl.

I understand there is nothing wrong with being bisexual or homosexual but I have found a girl that is offering me everything I have ever wished for in a partner and I want to if possible 'get rid' of any urges & fantasies I have that don't align with what I really want.

I am already in contact with my doctors regarding a 'check-up' to see if my ED issues are solely down to this and have an appointment in a few days as I write this...but my feelings in this regard have now become an issue that I am concerned about enough to seek help & advice.

Sorry for the essay but if anyone can help or advise then I would really appreciate this more than you'll ever know.