Kat, if you aren't considering hurting yourself, please know that people of all ages suffer from depression, doubt, and insecurity. Faith is not only challenging, but can be downright hard for some people. You will make it through the night: our Heavenly Father wants this. Your post is implying many things to me. First of all, at the age of 16- many young adults of your age group suffer from depression and doubt. This is not to sound condescending or mean- hormonal changes and imbalances can very well be a factor to your depression. You should speak with your parents/ guardians about this; you may need to speak to a professional. I am not trying to "imply" that there is something wrong with you. When you have feelings such as these, you should speak to someone for guidance and help. Though you obviously sound intelligent, you cannot always find all the answers on your own. I don't know or am not trying to imply your lifestyle, but if you drink or do recreational drugs, this can also lead to depression and doubt. So, do neither (if you are).
From experience, a relationship with God, like any relationship, takes time, trust, and knowledge amongst other things. Also, being a Christian is not just about reading God's words, but also includes missionary work. Have you considered volunteer work? Serving others can bring you to a closer relationship and understanding of not only God, but yourself, and the world.
As far as feeling doubt, doubt will always be in your life in some form. You cannot "give" in to doubt. This leads to depression, lack of self-esteem, lack of self-worth, and possible loss of spiritual peace and well-being. Do you go to church regularly? Are you part of any young adult groups or ministries? If not, you should join. When these feelings of extreme doubt or depression come over you, take deep slow breaths and tell yourself that you DO Have the Strength to handle this. As God for help: ask as many times as you need. Then, keep busy: talk to someone, clean your room/ car, etc. Sometimes distraction can be golden; if you are busy, then you may not have the time to feel bad or be depressed. What you may come to realize is that, God is the one holding you up and supporting you. You may FEEL far from God, but HE is with you always. HE is sending his blessings your way through your own good thoughts or other people that are trying to help you. Doubt is nothing but the devil: the liar/manipulator that is telling you that you are far from God. God is real and is with you. HE loves you and would never want or wish you pain including depression.