I have a significant other, but I'm not going to say "I love you"
That seems a bit off, do you love your partner?
I don't want to say I love you because in my eyes everything in this relationship is so unbalance
You should show affection to you partner regularly. It is not right to make them wonder if you even care about them.
Why should I say it when I don't feel it?
Truly, it seems that you're not in love and you and your partner deserve better. Break up, end it, as you both deserve better.