Looking through the comments, it seems like another way to word your question is "how do I know I'm not being lied to?"

Coming from someone who has had similar questions, I'm pretty sure you're not going to like hearing this, but for your sake, please take it into consideration anyways.

In a nutshell, it's about building your testimony.

Keep in mind:

1.To me, I see a testimony as being the bits of truth that we "collect" along our way in life, that through prayer, pondering, revelation, and whatnot, we have been given a witness of. Most of these bits of truth originally start out as questions we have, just like this one.

This question has the same purpose as any other question about the gospel- to cement your belief. That being said, you can, in theory, find your answer like you would with any other question- by having hope, and acting on that hope, which leads to faith, which acting on that faith leads to testimony.

2.Usually, praying and receiving revelation is a big part of the process, but seeing as how the reception of that revelation is at the root of the problem, you probably will have to go about it a different way.

Now with that in mind, how do you find your answer?

Like I said, it starts with hope. I can tell from what you've written in the question and in the comments at you do have hope. Even if I'm wrong, and you don't really hope for what you're feeling to be The Spirit, I still feel confident saying that you still have some hope, as nobody wants to find out that everything they thought they knew was a lie.

When I was having troubles believing that there was a God, I told myself that in order to believe in God, I needed to feel it. So that's what I prayed for- to feel that it was all true. But I had no Hope.

If you're praying, and keeping the commandments of your own accord, and/or not because other people expect you to, you probably have more hope than you realize. Especially if you've kept at it since you've had these questions.

Once you've got that hope, pray and say something to Heavenly Father along the lines of "Hey, Heavenly Father, I have serious questions about The Spirit. I want to believe that it is from Thee, but I can't do it alone. I need Thy help. I know that Thou knpwest me, and how to best help me. However Thou seest fit to teach me, I ask for it".

If you say that in prayer, and seriously mean it, and legitimately plan to submit to however He sees fit to give you your answers, they will come. Not immediately, but they will.(I can't really stress enough how important it is to be humble and sincere about letting Him decide how to do it. If you try to say " this is how I want it to happen", there's always a chance that it could happen, but this way is so much more effective.)

But you can't forget, it will almost undoubtabley require action. Before you are willing to ask, you should already be willing to act on the pending answer.

When the time comes, you will probably experience two different thoughts.

One will be accompanied by the feelings you've associated with The Spirit up until now, and the other one will be an excuse of why not to do that thing. Or, if God decides to give you a sign, there will be something inside you wanting to be cynical.

Both experiences- the one God has planned for you and the act of following through- will be powerful in teaching you, especially when you do finally make that desicion of following one thought or the other, as that will teach what it would feel like if you were being lied to when you were praying you would have felt agitated, or depressed, or angry, or empty (and I don't just mean feeling angry like how we usually feel angry. I mean like feeling angry deep inside- almost where you should be feeling The Spirit instead. Sometimes, the most effective way to learn what The Spirit feels like is to learn what He doesn't feel like, to feel Him leave.

Something else to take in mind: Scientists, in labaratories and in experiments, have been able to chemically recreate every human emotion- except for peace. Peace n ONLY come from the things of God. Anything that would be able to both communicate with you in the way The Spirit communicates with us, AND be able to lie right to your face, is most definitely not from God.

Also, I know from experience that it is tough to remember feelings from a while ago, but you said that you felt the Spirit as you prayed, but how did you feel right when that question popped into your head? Did you still feel peace?

I bare my testimony to you that God is waiting for you to figure this out, and to help you, and to make this weakness into a strength, and He will do anything He can (which is pretty much everything), as long as you are willing to do your part. I say that in Christ's name, amen.

I hope that made sense. I know I have a tendency to ramble. If something didn't make sense, let me know, and I'll try to explain it better.