New and need help

I think I have a severe case of OCD but I havn't been diagnosed. I have fears to do or not do certain things such as wash my hands, what clothes I wear, what I can eat and when, and even things like where to sit. I feel like if I do or don't do these and other things that bad things will happen. It's like there's this voice in my head telling me that if I were to do these things something bad would happen such as to stop liking the guy I like or that I'll end up hurting myself or someone else. I try not to let it control me but it does and it's really hard. There are certain things that seem to trigger it such as certain smells or tastes, and gets a lot worse if I have any caffiene.
Also I have lots of intrusive thoughts, such as cursing God and Jesus, inapproipriate images, or simple fears of something happening. I feel sometimes like I've committed the unpardonable sin and feel really scared about it, yet other times I completely think that God doesn't exist.
Another example is I was afraid to post this or join the forums because I thought something really bad would happen if I did.
Is there any advice or encouragement anyone could give me?

Thanks, flowerforever7! It does make me feel a little better to know someone else struggles with the same thing.

Thanks for your replies, everyone!
@dabro: so it's all just normal ocd stuff?
@adam: i also feel like if i do the wrong thing God won't save me. thanks for your prayers!

@joshicedogs: thanks! did the little voice just sort of go away on it's own, or did you start doing something different? and i have gone to my pastor about it and he's gotten me set up with a counseler...