Being with a girl

Kallia
So for starters I am in a very happy heterosexual relationship with a man that I plan on marrying. Though for years now I have wondered what it would be like to mess around with a girl. 
I asked my boyfriend if he thought it was cheating and he said "technically yes, but if it something you are interested in we can talk about it". I am not sure what to do now. I feel bad for even asking even though I think I would like to try it. It has been a few days and I haven't brought it up again with him because I am not sure what to say...
Any suggestions on what to do? Or anyone been in a similar situation?