Having fear when going into unknown territory is normal. Courage is having this fear and going into unknown territory anyway.
If this is your Mr. Right then he will wait--because that's what your Mr. Right does. Also, if you are his Ms. Right you too will wait for him--because that's what his Ms. Right does.
You said, "What if I am the one that screws it up?(I've made alot of bad decisions in alot of relationships.)" The simple answer is screwing up is a choice people make. Sometimes as you are aware it is hard not to screw up. It is a whole lot easier to avoid situations where a screw up might happen. If you never allow yourself to be in a place, situation, company of the wrong person(s) where a screw up might be possible then a screw up will never happen.
Best wishes to you!