Can I still go to Heaven if I kill myself?
No. Running away from problems through death isn't really a good solution.
Well since that would be murder then no, you can't. I can understand the desire to do it though. I struggle with that regularly when life gets too hard and heavy. I'm sorry that this even has to be a question in your mind. Hopefully life improves for you.
According to the Bible no, you'd go to hell. One of the 10 commandments says: "Thou shall not kill" and that also includes yourself.