I've been questioning my sexuality alot for the past 4 years. 
It started when I would chat to girl on tinder and online forums. I would also fantasize about girls and watch alot of lesbian porn. I sort of pushed these bisexual feelings and thoughts away and did not think much of them. I have a long term boyfriend right now and some how i am still fantasizing about getting with a girl. 

I started to think I was bi curious and have been thinking about it for a couple of weeks when I suddenly had a moment of unexpected realisation - my first ever sexual experience was actually with a girl.
In primary school I used to co-masturbate with my close friends and I always initiated it. We used to watch eachother rub ourselves and i remember liking it so much when I was little.

I have realised that these feelings towards girls may not really be anything new like i initially thought. But since I have not done anything with a girl since primary school - how can I know if i am really bisexual? 
Does these young experiences count towards my identity? 
I can't really explore with a girl now since I am already in a relationship with a guy. But it is frustrating me that I don't know who I am. 
Would you consider this being bisexual? Does sexuality form from a young age? Or am I really misinformed? 

Thanks xx