Hello and welcome to the site! you will find a lot of good feedback here. I'm sure some of the of the mono people here will not like what I have to say, but oh well, here it is.
I was also a mono for 50 years.....or you could say 30 years because I wasn't that sexual for the first 20 years. I was very set in my mono ideas. I stood firmly in the mono world and couldn't be swayed from it.
All the while, I'm noticing and acknowledging that monogomy doesn't really work any more and it doesn't really make sense either.
When I decided to give polyamory a try- two years ago, all of my relationships improved.....just sayin'....you're young and you're hanging on to monogamy which is simply not that sacred. Do you even know why you are hanging on to it so tightly??
The key to life is in being fully engaged and peacefully detached simultaneously and authentically in each moment.