Hello and welcome, everseeking.
A relationship with the LORD is not a guarantee of mental health any more than it is a guarantee of physical health. It does, however, give you an available and powerful outlet, when you can turn to the Most High with whatever is on your mind.
1 Peter 5:7 tells us to cast our cares upon Him (Christ) because He cares for us. The great thing about prayer is that it's not a set, ritualized system guided by rules and regulations. It is open and honest conversation with the LORD. The LORD knows your thoughts (Psalm 139:4) and He can certainly begin a work in you that changes the pattern of those thoughts. However, I think ignoring the help available all around - i.e. counselors and the like - is a mistake.
My suggestion would be to spend time in prayer and study to strengthen your relationship with Christ (because as RustyAngel said, hell shouldn't be a part of your mental equation), and in the meantime seek counseling from your pastor, or a Christian counseling center if you're not in a church. I think they would be able to help you with whatever this pattern is you find yourself in, while at the same time helping you on the path you walk with the LORD.