If you do, then you two should __seriously__ consider marriage counselling (both joint and individual), especially with a baby on the way. I don't know if this is your case or not, but many couples in trouble think that having a child will deepen their commitment to the marriage and make it stronger. Having a child has the _exact_ opposite effect. If your marriage is in trouble now, having a baby will probably destroy it unless you __want__ to get help and are committed to making your marriage work.
Having children is one of the most rewarding things that can happen to a couple. But it is also one of the hardest jobs you will ever have, and it's not a job you can quit. Unless you totally turn your back on your children you will always be a father, even if you're not a husband.
I'm going to guess that you and your wife have problems communicating with one another. I mean real, honest, heart-to-heart communication. You both need to be able to talk with each other about your needs, concerns, fears, hopes, dreams, etc. without the conversation degenerating into argument after argument. Marriage counselling will help you with that too. It can also help the two of you figure out if the marriage is worth saving.
Unless you have an open marriage, hobbying and being a "good husband (one that doesn't 'cheat')" are mutually exclusive. Now, if, by "good husband", you mean "provide and work towards maintaining a warm, honest, loving and stable environment and relationship with your family", then yes it's possible. You just better have a spouse that graciously accepts, or better yet wants to participate in, your extra-curricular activity.
At 29, you've got a long road ahead of you if you choose to stay in an unhappy marriage. The two of you will be utterly miserable. Good marriages don't just happen, they require constant care and feeding along with a good dose of hard work from both parties to make them work. If the two of you aren't willing to work at it, then get out, if not for your own sake, then for your child's. Two miserable people raising a child isn't in anyone's best interests.