A pregnancy is not a good reason to get married. A marriage won't hold two people together anymore than a child will. It will be one more thing to look back on and regret. The divorce rate in this country is amazing.
These aren't things you should rush into. Marrying someone doesn't magically solve anything. It doesn't make you love them more, or them you. If one of you decides you're unhappy, a marriage won't cure that. All it will do is complicate things if one of you decides to leave the relationship. And honestly, would you want your partner chained to you legally so s/he can't leave? That's not my idea of a happy relationship.
You can't undo becoming a parent. Short of giving him/her up for adoption, you are responsible for that child for at least the next 18 years. If they have special needs, you'll be responsible for them much longer. The financial needs a child has can not be easily met with a job acquired at the tender age of 16. A minimum wage job and a lack of a high school diploma will not get you far. You will be doggy-paddling in the ocean at best and drowning at worst.
Please ask yourself - what is the rush? Will things be the same or better in 5 years? If so, why not wait 5 years? If they'll be worse in 5 years, what would getting married or having a baby now do to prevent that? Babies add to the stress on relationships, they don't cure them.
What are your reasons for wanting a baby right now? Can you 100% honestly say that you can give your baby EVERYTHING s/he needs? Without relying on your parents? Without living under someone else's roof? Without borrowing money or requiring free child care from a relative? If you can't afford it now, there's little hope you'd magically be able to afford it in 9 months.
There's a saying: start as you mean to continue. Don't wait until something happens to be responsible. Go to school. Get your education. Enjoy your relationship without trying to rush forward. If he really loves you, he'll still be there in a few years. Get a job and save every penny you can. Work on becoming independent now. See if you can do it BEFORE you bring a child into this world. Keep asking yourself "Great! What else can I do?" Push yourself further. Expect more of yourself.
The big steps in life should never be rushed. Not if you want them to be successful.