Sounds like you're singing from your head the whole time, try singing with your diaphragm so you project your voice more. It doesn't seem like you have a naturally loud voice so you're probably going to have to try keeping your back as straight as possible so your air flows better. I'm not a great singer myself, but I used to be in choir so I at least know the basics. Also, the more confident you are, the louder you can be.