I can totally relate to your insecurity considering the faith. I´m also a Christian. When I´m under emotional stress, like I was during the last months (and I am still: divorce, problems at work, financial problems), I often think what if I go mad, hurt my child or my pets, say stupid things in a meeting embarass myself or others,..... the whole "program".
Recently I bought the book "The imp of the mind" that has been recommended here several times. (I could get it in German)
I want to tell you that I have come to the conclusion: if I´m saved in Christ, gave my life to Him, if I want to follow Him and be a good person, lead a spirit filled life, why should I be afraid that those things will happen to me? I mean, why should God let that happen? Me, going nuts out of the blue, when I believe that he has a purpose for my life?
You know, since my daughter was little, I used to pray with her every night, and I use to say a blessing and then aks God to cover us with his blood,(don´t know how to say that better in English, hope you understand). Shouldn´t that be enough?
As a Christian I also believe that there is an enemy who wants to tear me away from Christ, who wants me to feel like crap so badly that I don´t dare to come to God, right?
And another helpful thought: when I´m busy and destracted, normally I don´t have weird thoughts, at least not 24 hours day. So why should I lose my sanity all of a sudden, right in that moment, just because I THINK of it? Thinking isn´t magic, if it were, then people must drop dead just because I think of it, or wish they did... oh, if my thoughts really had that power, my co-worker would already have ended up on the cemetery....

I know that it isn´t funny when we have these thoughts, but sometimes it´s good to see some humor in it.... God bless you all!
Susanne