Fighting i feel is healthy in a relationship.
My boyfriend and i have a fight once in a while, and it gets out the frustration we are feeling towards each other, and doesn't keep things bottled up. And we talk openly about things that we might not like that much about each other.
Talking about things is healthy to do, so when a fight does occur, you aren't bringing up old subjects that are in the past.
You should talk about the things you feel are small but still irritating, and by doing this, it could help in the future for them not to be repeated and you both could learn from these things too.
Maybe if you two talk about how you both feel and get out what you both do that bugs you, it could help you two not fight as often.
Your both each others first, and im sure dispite the fights and all you both love each other, but want to have sex with different people..maybe your sex life needs to be spiced up a little more, and that is why you both feel the need to have sex with different people.
Or maybe the whole relationship has become a little dull because you two have been together for so long, but that does not mean it should be ended now, and that you two should see other people, you just need to livin things up a little.
At chapters there are alot of little books on sex positions, how to spice up your relationship and love life, you just might need to add a little hot sauce to your relationship right now.
I dont know how you feel exactally, because i am content with my relationship, but i do know how it feels when it has hit a boring spell. There are ways to make your relationship feel new and fresh.
I would not jump into having sex with other people be it people of the same or opposite sex, even if you condone it on both parts..it just doesnt seem right if you are in a relationship which even though you are not in a married one, you both pretty much agree to be faithful to one another..