What powers? Are you referencing that as abilities? Are you talking about spells?
If you are referring to things towards the lines of being a psychic or medium then it is a matter of learning more about such. If you had so called "powers", I would imagine you would be able to control them; however, you may not know much about or understand them.
In the way you are describing powers then that is not a spell. A spell, along with other magical workings, is a way or power of influence. This way of influence is something that everyone has the capability of. This does take time, dedication, and patience; however, not all magical workings may follow the same course. Magic comes in many ways and is performed differently among cultures and individuals.
My best advice for you would be to be patient and keep trying your best. Learn as much as you can. Not every spell will work and it could be a while until you successfully cast a spell. You could look into other methods such as directed prayers? Many things may fail if you try too hard and over think it or if you just put too little effort into it and it falls apart.
The effects of spells may happen but it might not be in a way you expected. This can happen due to not being very descriptive with your intentions. Plus nature works in ways beyond our understandings. Maybe your spells never worked because it was not something you needed. It could of been something you wanted and nature knew that. It may of been because you kept begging for it by contiousily doing the spell. I do believe all those things can affect the outcome of a spell. What do you think?
You may not be doing anything wrong either. I would recommend that you look at all the possibilities that could go into affect with such.
"These spells have not worked, yet at the same time it seems like spells I have not cast have acted" - Can you explain this a bit better?