Women recognize only one happiness, love and be loved. Women expect men who become their partners give them attention, concern, understand them, treat them well, etc. And if women cannot get what they expect from their partners, maybe they will looking for it from "the another man".
I was the another man.
But not in a marriage. My wife had a boyfriend when we were in friendship, but she was closer to me than to her boyfriend. I gave her everything that she expect like concern, attention, etc. Everything that she never got from her abusive boyfriend who treated her badly.
I did it not because I expect her, but because she's my friend, and I am a man who have empathy and concern to women. My friendship with her was real friendship, I always avoid physical contact.
That made her fell in love with me, and it's became a problem after I proposed marriage to "the girl from south" and the girl who now becomes my wife could leave her boyfriend. She was very jealous because she tought, another girl grabbed someone who belong to her. Frankly, I was so shocked because I never thought she would fall in love with me.
But finally fate determined, she married me after "the girl from south" left me.
Back to your case, sis. I understand if you were looking for attention from another man. I know you feel disappointed with your husband. And I will not blame you if you fall in love with that another man.
But, sis, your situation is different. You are already married and have a kid. So, you should stop contact with that another man. I know it will hurt you, but you must be strong. I know you cannot do it (leave that man) for your husband. So, do it for your kid. You are still in a marriage, remember?
Try to accept the reality that another man is not for you.
Don't worry about that another man. If you stop contact with him, maybe he will miss you. But not for long time. I think he just a man who has empathy and concern to his friend on internet, not a man who want to marry you. But his care and attention to you make you assume he expect you and it made you fall in love with him.
And one important thing. Keep your feeling to that another man and your online relationship with him as a secret. People around you do not need to know about it, because maybe they will judge you. So, if you want to seek an advice from people around you, just seek advice to motivate your husband to change himself.