You've got to be careful, unless you want to leave your DH. I had a 'thing' with another man a while back. At first it was just talking about how attractive we found each other. That seemed fine, I didn't feel in danger of doing anything else at that time, but the thought had been planted in our minds. Next it was casually putting our arms round each other and then dancing close, which seemed slightly 'naughty' but we didn't feel too guilty. We actually talked about whether what we were doing was crossing the line and kept persuading ourselves/each other that it wasn't because we wanted to carry on and not feel too guilty to carry on.
So it got more and more intimate until it went 'all the way', at which point he put a stop to it and I got hurt because I had got more and more emotionally attached without even realising until it ended.
I deserved for it to hurt of course and I deserved it that I had to suffer it on my own (couldn't tell DH, had to carry on as normal at home and blame my crying, when I couldn't control it, on other things). Friends weren't going to be very sympathetic when DH had done nothing to deserve it and I should know better than to be so stupid at my age.
What I'm trying to warn you about is even if you don't feel you are being unfaithful at the moment, what you are doing could make you in danger of doing more, and the more you do, the harder it is to stop because being in lust/love is like an addiction. Then when it ends it can hurt so much (and for a long time) that it really wasn't worth it, and if your DH found out, even worse, life destroying, just because of an addictive craving for the excitement of it, which might feel meaningful at the time but really it is just your body's drugs taking over.
I know in future I will treat the danger of falling in lust/love with someone else with as much caution as being tempted to try an addictive drug. Don't even start it, unless you want to leave your DH.
Maybe other people aren't as prone to the addiction of it as me, I don't know.