First and foremost, keep hanging in there hun.
Getting pregnant at 16 is a big deal so be gentle with yourself, think things through, and don't stress too much. Everything will work out somehow in the end.
A good place to start would be to tell your parents. Hopefully, they can be supportive and help you figure things out. And you also need to tell the baby's father. He deserves to know. But remember, teenage boys can be quite stupid and he may not react well. Just prepare yourself for that. In time, he may come around. The same is true for your parents if they react badly at first. As for your friend, I think that you should tell her. Although you may want to wait until you've had time to come to terms with everything and have a plan, etc. It'll make dealing with whatever reaction she has easier.
Finally, if you want to keep the baby, then do it. It will be challenging but it's entirely possible to have and raise a child at 16. Not everyone will be supportive of it, but if it's what you want to do, then do it. You can.
I got pregnant with my son shortly after I turned 16. I had only been with his dad for a couple weeks at the time and it came as a huge shock. I was in denial for probably a month before I even decided to test. It was all just incredibly stressful and I was freaking out. Fortunately, my mom was supportive when I told her. Other family members weren't quite so supportive. But in the end, everyone came around. My son was born a little more than a month before my 17th birthday and he's been the absolute light of my life ever since. It was really hard at first, I won't lie. It was a hard to learn how to be a parent and how to be in a relationship with his dad and how to balance everything. But I went back to high school in the fall when my son was 5 months old and graduated on time (I was pregnant with my second by the time I graduated as well). I'm now 24 and my son is 8. It's been a bumpy road to get to where we are now, but having him is still the best decision I've ever made in my life.
I'm sorry for writing a novel - I figured it might help if I told a little of my story, too. If you need anyone to talk to or want some advice, feel free to PM me. I've been in a similar situation and might be able to help some. If anything, I'm a good listener.
So take a deep breath. Everything will work out.