you're 21 and you've been married for 3 years already... i won't give you the lecture but you probably already know that you're in over your head and you tried to jump too far ahead in your life.
now the situation is that you're husband sleeps around while he leaves you at home with the child. does he know that you know about his other sexual actions or does he feel that he keeps this secret covered up fairly well? if not, then i believe you might want to talk to him because why should you put your life on hold while he goes out and has all the fun?
i know that it when you think of your child, you don't want in any way to hurt them, but you have to also watch out for yourself in these situations. is it fair to you and your child then he neglects you? he might be a good father, but what impression does this leave on the child whether or not they find out about their father having an affair? first of all, you should confront your husband and let him know that he is being unfaithfull.
however if he already knows that you know and doesn't care about you, then why should you return the love? i know that i wouldn't. having an affair with someone online might seem like a temporary excitement but you know that it won't lead to anything. if you're just looking for a good time then by all means go for it, but remember that you are an example for your child. they will follow is your footsteps reguardless if you want them to or not. raverboy
...this is just my perspective on the situation...