Is it normal my ex is messing up my head?

You're heart is a fictitious thing. Everything is in your mind and therefore subject to reason.

These doubts your having, if they keep coming up it is because you don't believe the so-called logic you're telling yourself. Nobody here can tell you what to do based on the limited information you've given, their advice is loaded with personal biases. Make a decision either way and give it your all. Both options have the potential to be wrong, just ask yourself which you will regret more if you don't choose it.

This is actualy something i'm experiencing at the moment.
I dated a girl a while back,roughly 3 yrs or so.We are both dating other people now.When we were dating we came to the conclusion that we are each other's soulmates.I still believe she is and she is of the same disposition. How do we know this? After we broke up everytime we meet (same profession small town) we end up having sex.Needless to say the sex was and is still great.We rarely talk on the phone but when we do we always go back to the 2/3 hr flirting phase phone call style. But,..i will never get into a relationship with her again.Simply because we can't go a week without a verbal,emotional and physical rollacoster. Go with logic and basic common sense on this 1 OP.Opposites attract...so long as their is enough underlying similarities to tie them together.

If you don't get what you what from the relationship why stay. If you are unsure, list the reasons why you still want her and think about if those reasons are enough that they will make you both happy. Be honest to yourself! If its because it is a recent thing, you are going to feel some hurt. Lack of respect for your partner is never a good thing. Remember, if your not happy in yourself, it's easy to give too much too easily.

Sometimes opposites attract, but only for so long. Do not let yur emotions rule over logic please.

Ask her out again. Opposites attract and dating someone out of your element will benefit you and her. You both have a lot to learn from each other. :)

You already know it won't work.

You can't have a decent relationship with her, that is why you dumped her. If the reasons you dumped her change, maybe then consider a relationship, otherwise it is just destined to fail.

It sounds like you two need some time apart.

"A. Following my heart, ignoring our incompatibilities, and asking her out again."
I really don't think it's your heart you are following. I think it's your dick!
You should probably cease all contact with your ex and go find someone else. Once you are getting laid regularly by another girl, your ex will fade from your mind like a bad dream.

Do you know The Akward Yeti? Heart is so naïve.

She's your ex for a reason. Move on with your life.