Assalamu Alaikum!

Hello everyone, I'm a new member here. I want to bring up possibly one of the strangest things you fellow brothers and sisters may come across, but I feel on a personal level I need to discuss this. 

So it goes like this- I'm a young Muslim, not the most dedicated  nor committed, but I do try. I try to make sure I get my 5 prayers done, and I try to abide by the Islamic way of life, much as I can. However, sometimes my conscience questions itself. Often I will feel the need to be a better Muslim, when I have some wordly motivation in mind. And this happens all the time; When I was younger, I would make a markedly greater effort to make sure none of my prayers were delayed when I had exams coming up, I would pray with a greater level of sincerity, and frankly be a better Muslim than I was until then, temporarily. Unfortunately, I've never been able to grow out of this habit. Even now, I find myself paying the beggar extra, never lying, praying right as the Aazan is called because I know my Yale decisions are coming up. I know and understand that this added sincerity is entirely dishonest, because I am doing this only to please Allah because I want him to be generous with his worldly gifts for me. Often, I make a resolution to be the exact same Muslim before and after any such "big day" but I end up failing. I console myself saying " Am I not supposed to be the (extra) good Muslim I (temporarily) am anyway? Will I not pray as fast as I can now that there is something bugging me in my head, making me do it?"

And as a result of that line of thought, I end up powerless to this extremely annoying habit I want to get myself rid of it. Praying an extra few Nafl Rakat and making dua for something you want is one thing, but having fluctuating levels of sincerity to your God and religion, I feel, is another. I find it exceedingly selfish of me, but I cant/dont do much about it. Anyone else ever face something like this? Any advice on what to tell myself to fix this strange problem?