I'm going to confess my feelings to another girl while in a relationship
Why do you want to confess your feelings to a girl other than your partner?
It is because of the fact that she makes me feel good around her and she's so hot.
It's not wrong to have feelings for someone, but you should only be in a relationship with one person at a time to avoid hurt feelings and jealousy.  If your partner doesn't approve of you having an open relationship, you should not be seeing other people behind her back because it can cause a lot of heart brake and drama.
I'm blinded by love and  there's no way in hell I'm going to stop now.
If you feel this way about the other girl, you need to break-up with your girlfriend first. It is only fair to her.