I'm in a steady and very happy relationship but can't stop thinking about another woman.
Are you wanting to risk your relationship to be with her?
I wan to sleep with her at least once.
It's wrong to have this thoughts when you are supposed to be in a committed relationship. Your partner might get angry with you if they know you are obsessed with someone else. You can't expect to cheat on your partner when you want.
I don't care about any of that because I love my partner.
If you love her, then stop with these carnal desires. Refocus on making her happy.