Warm welcome to CC Forums, Emma! We are so glad you came. I really like these forums a lot. I was unsure when I was younger also. The really good part starts when you begin to become sure. God wants to make you that way, but first you have to believe that Jesus really really loves you. Then you trust Him. That will make it possible to completely surrender to Him. Then He can give you that blessed assurance. It is wonderful.
We are not born with assurance inside because Adam sinned. Fortunately Jesus died on the Cross so we can have it again. John 3 tells us about our sin and Jesus' sacrifice. The main thing to remember is that Jesus loves you, Emma. We love you too. God bless you.
John 3
3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
3:17 For God sent not his Son into the world to condemn the world; but that the world through him might be saved.
3:18 He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
3:19 And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil.
3:20 For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved.
3:21 But he that doeth truth cometh to the light, that his deeds may be made manifest, that they are wrought in God.