Well, I haven't quite been in your position, but my advice to you would be what the other ladies mentioned.
Also, there are resources in your community I'm sure that can help you out with formula and other baby supplies (WIC, etc.). Maybe you can get some hand-me-down items from an older friend or relative. There are also ways you can finish school, like night school or GED classes. Finishing school is *extremely * important, because if you don't, you will have a hard time getting a very good job and may struggle financially forever.
At 15 there are many jobs you can get, waitressing is probably one of the best. I started waitressing when I was 15, and it was pretty good money. Also, when you are pregnant (and start showing) you will get better tips. =) From my experience, anyway.
Good luck to you!! And stick around, this website is a great place to ask questions and find people in similar situations.
Kimberlee is right. Saving money is definitely the way to go, and also garage sales and second-hand stores are great too.
You really need to talk to your family, if you haven't already. I know it'll be hard, but sometimes the best thing is to just grit your teeth and tell them. Your boyfriend sounds like he's a decent kinda guy- I really hope he's willing to stand by you and the baby!
It sounds like you're really looked into all of your options. I've never been in your situation exactly, but I know how exciting it is to be having a baby, and I hope everything works out for you!
Well, it's not impossible but it's not going to be easy. I'm sure with the support of your family and your boyfriend you'll get through it. The best thing would be to SAVE YOUR MONEY! It takes a lot of money to raise a baby, and buy all the essentials like a crib, diapers and wipes every week. You'll need all the money you can get. After you are past the first trimester (12 weeks) you can slowly start buying things that you will need, so that way you're not 7 months pregnant and have to worry about buying everything at once. I'm sure you'll get a baby shower, and that should help a lot too! It's good that you're taking responsibility for your actions, and so is the father, but just know your whole life is going to change, no more going out with friends all the time, it's going to be all about your little one, which is exciting and scary. I hope the best for you and your new family!