Try to break the news to him gently as possible and let him know that it just wasn't meant to be this time around. If he loves you he will understand and the two of you can get through this together.
Sometimes when we really want to be pregnant or worry about being pregnant, our bodies and minds trick us into feeling symptoms and thinking we are pregnant.
At 16 you should really try waiting a few years. Think of all the great things you can do with your boyfriend in the mean time to grow as a couple. You can go on trips, finish up school, get a great job to take care of your child one day, and spend tons of time with your friends. When you have a baby, achieving these things are much harder. Enjoy your life together as a couple of two while you still can and try not to worry about it