I thought this was going to be an herbal remedy issue, but clearly is not. Seems to me you might be thinking of guilt when you try the spells. If you are, or were, in a Christian home, I can understand. You are getting nervous about this nagick, and causing your own belly ache. Sounds weird, but I know people who can make them selves sick to get out of doing something or to not have to go somewhere. This could be happening to you, only you are doing it over nervousness of doing spells.
Since you said you are starting, you need to learn and apply the basics of magick.
Here are some links to help you:
http://www.spellsofmagic.com/read_post.html?post=71692-Starrie's "Starting Out" post
http://www.spellsofmagic.com/read_post.html?post=483942-AwakeTooLong's "Basics: Expanded" post
http://www.spellsofmagic.com/read_post.html?post=251089-Basics by Sagesk
Also about.com is a good site for all kinds of info. Once there, put Wicca basics in the search bar. It will take you to basics of magick, too. I was on it for hours just looking and reading. And copy and pasted a lot of things to my computer.