Ah, yes, one of Satan's most powerful tactics is causing us to doubt. The thing is, we needn't concern ourselves with these thoughts. The Bible tells us, time and time again, that the Lord is our provider! And we can have confidence that this is true.
You're right about God not being finished with you yet. What you are today is not what you will be tomorrow. I can firmly attest to this as being true. A year ago I used to struggle with anxiety, and to the point it would become downright tormenting in certain situations. Overcoming it on my own was an extreme battle. I couldn't do it. No matter how hard I tried. So in an act of desperation, I finally gave my anxiety over to God three months ago and was completely set free! Really, I'm doing things now I would have never imagined I'd be doing. For I would have been either too scared or unsure about my capabilities. I'm also a lot more talkative and if you personally knew me, you would have to agree that's a miracle in itself.
So, yes, you're completely right that God is not finished with you yet. Of course, you should be seeking God on this matter as much as you can. After all, He is the one who has called you to do this. He knows what will prepare you best for this life and what you must do next.
Likewise, I'm not speaking about seeking Him for a month then giving up after not receiving any response. No, I mean full out persistence! Seeking him daily and waiting patiently with faith that He's going to lead and answer you regardless if you might have to spend a year seeking! If you want to work in ministry, you'll have to learn to be a listener first.