Yes it is cheating. If you are doing something you believe your partner would e uncomfortable with or outright hurt it is an emotional betrayal. One should be investing this time into bettering themselves and their relationship, not building new ones. I'm devastated by what my partner has done & it's only been two weeks since he started talking to her and its not as bad as this one. I still none the less am heartbroken and feel completely betrayed. I believe it violates our relationship. Good luck to you. No one deserves to feel like this.