Just relax.
You truly are in for the ride of your life, so try to enjoy it as it is happening. Stay in the moment.
That being said, a few pieces of advice...
1. Try to enjoy your pregnancy, its not always gonna be awesome, but (ideally) its only gonna happen a handful of times, so go with it. Reading was the best therapy for me. Someone mentioned Jenny McCarthy's books. "Belly Laughs" is the one about pregnancy and I thought it was hilarious. "Baby Laughs" goes through the first year - it was funny, but not as funny. As far as reading goes, I teetered between learning enough, and learning too much - so don't go too crazy - knowing too much has a tendency to make people paranoid.
2. So wow... pregnancy... you are in for certain things now. You are 17 weeks along now, so no doubt people are asking you if you are getting morning sickness. If you are not tiered of this question yet, you will be soon.
3. As you really start to show, people will ask if you have or plan to find out the sex... and then of course which you prefer. Unfortunately I really wanted a boy (grew up w/ no brothers and 3 sisters) and told people my preference right off the bat. So when I found out I was having a girl (and that upon finding out I cried for 3 hours,) people acted really uncomfortable around that subject for a while. My advice is to tell everyone you don't care what the sex is, regardless of your true feelings... because let's face it, you can't change it now, so your preference doesn't matter anyway.
4. So then after you find out the sex, the rest of your pregnancy will be plagued by "What names have you picked?" I also suggest keeping this to yourself. People get really weird about names and will feel compelled to tell you their crappy opinion on it. What worked best for me was making a joke. Whoever was asking me, I would say I was thinking about naming it that. That always makes people laugh. Towards the end I told people I would let them know when I introduce the baby to them. Of course I only learned this after I told my mother my name choice (Sophia) and then she badgered me my whole pregnancy about not naming her that. Its no one's business but you and your husband's.
5. Then as you really get close to delivering people will ask you if you plan to breastfeed. Most people will tell you breastfeeding is best, and of course it is, but don't feel bad if it doesn't work out - that's why bottles and formula were created in the first place.
If you do plan to breastfeed, or are on the fence, take a class while you are pregnant to help you decide. They offer them at the hospital for a small fee and go into detail about what to expect. Even if you take a class, get as much help as you can at the hospital. A lactation consultant should visit everyday, so batter them with your questions and have them watch you to make sure you're doing it right. I know this sounds weird, but breastfeeding is way harder than you think it is (not the act of it, but everything that goes along with it.) Also, I suggest keeping an bit of formula and a few bottles on hand just in case.
6. Then they will ask you about the epidural. The epidural is a HUGE debate and people ALWAYS have a strong opinion about this too. My advice is to also skirt this topic - don't tell people you are committed either way. Its your first delivery, so claim stupidity, and say "I'll get one if I need one," because the truth is - you will. If you really feel you need one, or if you end up w/ a c-section, they will give you one regardless, so don't spend too much energy thinking about it.
7. The one thing I hated when I was pregnant was... older women LOVED to share their terrible stories (usually labor stories.) Especially as you get closer, tell people you only want to hear GOOD stories. There's no sense in scaring yourself now - you have very little control about your labor and delivery anyway, so fill your head with pretty thoughts. Pregnancy hormones make you paranoid enough as it is, you don't need people's stupid stories making it any worse.
8. You are young, so (as long of the rest of your life is fine/normal) the hardest thing will probably be adjusting to life as a married woman and then... life with a baby. BIG ADJUSTMENTS! I personally found getting a therapist to be very helpful.
9. I suggest only venting about married life/baby life to people that are married and/or have babies. Your single friends will try to understand, but let's face it... they won't. It will be very hard for them not to judge you/pity you /whatever, so save yourself and find people that are in your situation to talk to. My friends are all in their late 20s/ early 30's w/out babies. I only have one friend that is married. Needless to say I've found it hard share my life with them. They are busy talking about partying (which I couldn't care less about) and all I have to talk about is the color of my 6 month old daughter's last dirty diaper (which they pretend to care about, but really that just sounds gross to someone that doesn't have kids.) So get some friends that are in the same situation as you - it will make life way easier.
Good Luck honey :)