Not necessarily. If you want to know what a 'good thing' is .. It would have more to do with practicing safe sex and not getting pregnant at all. THAT is what would be REALLY good.
But, in any event, if it happens .. There are very basic but critical reasons for getting married .. and being pregnant is not one of them.
You have to be ready and mature enough to be able to commit to someone .. for the long term... NOT just temporarily. Too many people have very unrealistic ideals about what marriage is. Often due to their young age and immaturity. They still have a child's perspective in a grown up world. They easily confuse fantasy with reality. They rush into a marriage only to have it turn into something horrible. THAT doesn't not do anyone any good .. especially a child. A child needs to be nurtured in a loving environment..Not hostile.
Not necessarily. Compounding one mistake by making another is never a good idea. If the relationship wasn't headed in the marriage direction before the pregnancy, the baby shouldn't make any difference there. Don't give that baby the job of keeping the two of you together. That baby should ideally be the focus of both of you now; if it is meant to be, the relationship between the two of you will progress accordingly.
It depends on who the guy is. You can't just automatically marry someone because it's a big decision to make and a gift. You're going to have a child, and if your child grows up with a horrible father, that would mix up their life. In other words, if he really loves you and shows respect, maybe you could have a good family. It all depends on who your husband is.