Relationship question! Guys...advice?

I have been with my current boyfriend for 8 years now, we are very much in love despite a break up and some arguments in between (like most relationships). we have been very happy lately and it's been great between us, I love him a lot. Last summer however, my bf broke up with me for a few weeks in the summer and in this time my group of friends recruited one of their old highschool friends into the group.. we hit it off instantly and I would have dated him except for the fact that I was still hung up on my boyfriend and did want to get back together with him when it all came down to it. Despite this we were still very flirty with each other and people around us thought we were dating because of the chemistry between us, he is the only guy ive even considered dating other than my 8 year boyfriend...and he really liked me too. It has been like 8 months since summer ended and our little fling ended but we still talk relatively often as we are still friends. I think about him a lot though and I just found out he is kind of seeing a girl who is a trainer and has her own business or something..i feel like crap. is this really bad...what should I do...my heart is kind of pulling in two different directions..when I got news of this I felt a degree of devastation and it kind of felt as if this were news of a recent ex-bf getting a new gf...that's no good. Can anyone give me some advice on what they think I should do or if they've experienced something like this. [please take into consideration how i feel and telling me to break up with my boyfriend would simply be an insensitive answer]