Really until you see a doctor its never for certain. As for other ways you can give it up for adoption since you don't want an adbortion. My suggestion would to be to look into adoption agencies they will help you though out the whole thing and get support ( or let him know) from the father. He might be ready even if your not, also your parents and other members of your family might be interested in adoption your baby. Sorry to hear your not ready but that would be the best thing to do.
But first ting tomorrow contact a doctor, ( if you can't afford one you can get help from may different places). Then if you really are not ready start looking for a parent for your baby. If you look into this now you don't have to worry about it later. No heavy lifting, take it easy, but defenatly go see a doctor.
If your scared talk to him/her they will help you... There is alot of support whether you think you have it or not. I was young ( 18) when I had my first and I wanted to keep my baby, my parents supported me 100 % though they didn't approve but they were there and thats what you will need.